patch 8.0.1268: PC install instructions are incomplete

Problem:    PC install instructions are incomplete.
Solution:   Update the instructions. (Ken Takata)

src/INSTALLpc.txt

@@ -16,7 +16,7 @@ XP/2003/Vista/7/8/10).  There are also instructions for pre-XP systems, but
 they might no longer work.
 
 The recommended way is to build a 32 bit Vim, also on 64 bit systems.  You can
-build a 64 bit Vim if you like, the executable will be bigger and Vim wan't be
+build a 64 bit Vim if you like, the executable will be bigger and Vim won't be
 any faster, but you can edit files larger than 2 Gbyte.
 
 
@@ -42,7 +42,7 @@ Contents:
 
 The currently recommended way (that means it has been verified to work) is
 using the "Visual Studio Community 2015" installation.  This includes the SDK
-needed to target Windows XP.  But not older Windows versions (95, 97), see
+needed to target Windows XP.  But not older Windows versions (95, 98), see
 |msvc-2008-express| below for that
 
 
@@ -53,6 +53,10 @@ We do not provide download links, since Microsoft keeps changing them.  You
 can search for "Visual Studio Community 2015", for example.  You will need to
 create a Microsoft account (it's free).
 
+When installing "Visual Studio Community 2015 with Update 3" make sure to
+select "custom" and check "Windows XP Support for C++" and all checkboxes
+under "Universal Windows App Development Tools"
+
 
 Visual Studio
 -------------
@@ -285,17 +289,11 @@ your AUTOEXEC.BAT file with a line like:
 
 or on NT/2000/XP, go to the Control Panel, (Performance and Maintenance),
 System, Advanced, and edit the environment from there. If you use msys2
-compilers, set your installed paths:
+compilers, set your installed paths (normally one of the following):
 
-    C:\msys2\mingw32\bin
+    C:\msys32\mingw32\bin   (32-bit msys2, targeting 32-bit builds)
-or
+    C:\msys64\mingw32\bin   (64-bit msys2, targeting 32-bit builds)
-    C:\msys64\mingw32\bin
+    C:\msys64\mingw64\bin   (64-bit msys2, targeting 64-bit builds)
-
-for 32bit. And 64bit:
-
-    C:\msys2\mingw64\bin
-or
-    C:\msys64\mingw64\bin
 
 Test if gcc is on your path.  From a CMD (or COMMAND on '95/98) window:
 
@@ -430,9 +428,9 @@ And if you use msys2 to build python support (as one line):
         DYNAMIC_PYTHON=yes
         PYTHON_VER=27
         DYNAMIC_PYTHON_DLL=libpython2.7.dll
-        ARCH=x86-64
         STATIC_STDCPLUS=yes
 
+(This is for 64-bit builds.  For 32-bit builds, replace mingw64 with mingw32.)
 You will end up with a Python-enabled, Win32 version. Enjoy!
 
 
@@ -590,7 +588,7 @@ E.g. When using MSVC (as one line):
 Or when using MinGW (as one line):
 
     mingw32-make -f Make_ming.mak
-        LUA=C:\projects\lua53 DYNAMIC_LUA=yes LUA_VER=53
+        LUA=C:/projects/lua53 DYNAMIC_LUA=yes LUA_VER=53
 
 
 Or when using Cygwin (as one line) (untested):
@@ -622,7 +620,7 @@ E.g. When using MSVC (as one line):
 Or when using MinGW (as one line):
 
     mingw32-make -f Make_ming.mak
-        PERL=C:\Perl DYNAMIC_PERL=yes PERL_VER=522
+        PERL=C:/Perl DYNAMIC_PERL=yes PERL_VER=522
 
 
 11. Building with Ruby support
@@ -684,12 +682,12 @@ config.h and Ruby's DLL name. Here are the steps for working around them:
 
     Note that ruby_2_4 is the branch name for Ruby 2.4.X's source code.
     There is no need to build whole Ruby, just config.h is needed.
-    If you use 32-bit MSVC10, the config.h is generated in the
+    If you use 32-bit MSVC 2015, the config.h is generated in the
     .ext\include\i386-mswin32_140 directory.
 
   3) Install the generated config.h.
 
-      xcopy /s .ext\include E:\Ruby24\include\ruby-2.4.0
+      xcopy /s .ext\include C:\Ruby24\include\ruby-2.4.0
 
     Note that 2.4.0 is Ruby API version of Ruby 2.4.X.
     You may need to close the console and reopen it to pick up the new $PATH.
@@ -712,7 +710,7 @@ Using MinGW is easier than using MSVC when linking with RubyInstaller.
 After you install RubyInstaller, just type this (as one line):
 
     mingw32-make -f Make_ming.mak
-        RUBY=C:/Ruby22 DYNAMIC_RUBY=yes RUBY_VER=22 RUBY_API_VER_LONG=2.2.0
+        RUBY=C:/Ruby24 DYNAMIC_RUBY=yes RUBY_VER=24 RUBY_API_VER_LONG=2.4.0
         WINVER=0x501
 
 If you set WINVER explicitly, it must be set to >=0x500, when building with
@@ -749,7 +747,7 @@ E.g. When using MSVC (as one line):
 Or when using MinGW (as one line):
 
     mingw32-make -f Make_ming.mak
-        TCL=C:\Tcl86 DYNAMIC_TCL=yes TCL_VER=86 TCL_VER_LONG=8.6
+        TCL=C:/Tcl86 DYNAMIC_TCL=yes TCL_VER=86 TCL_VER_LONG=8.6
 
 
 13. Building with Terminal support
@@ -777,13 +775,14 @@ The Windows 3.1x support was removed in patch 7.4.1364.
 15. MS-DOS
 ==========
 
-The MS-DOS support was removed in patch 7.4.1399.
+The MS-DOS support was removed in patch 7.4.1399.  Only very old Vim versions
+work on MS-DOS because of the limited amount of memory available.
 
 
 16. Installing after building from sources
 ==========================================
 
-[provided by Michael Soyka]
+[provided by Michael Soyka, updated by Ken Takata]
 
 After you've built the Vim binaries as described above, you're ready to
 install Vim on your system.  However, if you've obtained the Vim sources
@@ -809,17 +808,54 @@ correct directory structure.
   new binaries you created above into "vim80":
 
      copy src\*.exe vim80
-     copy src\GvimExt\gvimext.dll vim80
+     copy src\tee\tee.exe vim80
      copy src\xxd\xxd.exe vim80
 
-  C.  Move the "vim80" directory into the Vim installation subdirectory
+  To install the "Edit with Vim" popup menu, you need both 32-bit and 64-bit
+  versions of gvimext.dll.  They should be copied to "vim80\GvimExt32" and
+  "vim80\GvimExt64" respectively.
+  First, build the 32-bit version, then:
+
+     mkdir vim80\GvimExt32
+     copy src\GvimExt\gvimext.dll vim80\GvimExt32
+
+  Next, clean the 32-bit version and build the 64-bit version, then:
+
+     mkdir vim80\GvimExt64
+     copy src\GvimExt\gvimext.dll vim80\GvimExt64
+
+  C.  Copy gettext and iconv DLLs into the "vim80" directory
+  ----------------------------------------------------------
+  Get gettext and iconv DLLs from the following site:
+     https://github.com/mlocati/gettext-iconv-windows/releases
+  Both 64- and 32-bit versions are needed.
+  Download the files gettextX.X.X.X-iconvX.XX-shared-{32,64}.zip, extract
+  DLLs and place them as follows:
+
+        vim80\
+            |   libintl-8.dll
+            |   libiconv-2.dll
+            |   libgcc_s_sjlj-1.dll     (only for 32-bit)
+            |
+            + GvimExt32\
+            |   libintl-8.dll
+            |   libiconv-2.dll
+            |   libgcc_s_sjlj-1.dll
+            |
+            ` GvimExt64\
+                libintl-8.dll
+                libiconv-2.dll
+
+  The DLLs in the "vim80" should be the same bitness with the (g)vim.exe.
+
+  D.  Move the "vim80" directory into the Vim installation subdirectory
   ---------------------------------------------------------------------
   Move the "vim80" subdirectory into the subdirectory where you want Vim
   to be installed.  Typically, this subdirectory will be named "vim".
   If you already have a "vim80" subdirectory in "vim", delete it first
   by running its uninstal.exe program.
 
-  D.  Install Vim
+  E.  Install Vim
   ---------------
   "cd" to your Vim installation subdirectory "vim\vim80" and run the
   "install.exe" program.  It will ask you a number of questions about

src/version.c

@@ -761,6 +761,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1268,
 /**/
     1267,
 /**/