patch 8.2.4856: MinGW compiler complains about unknown escape sequence

Problem:    MinGW compiler complains about unknown escape sequence.
Solution:   Avoid using a backslash in path. (Christian Brabandt,
            closes #10337)

.github/workflows/ci.yml

@@ -364,6 +364,8 @@ jobs:
       LUA32_URL: https://downloads.sourceforge.net/luabinaries/lua-%LUA_RELEASE%_Win32_dllw6_lib.zip
       LUA64_URL: https://downloads.sourceforge.net/luabinaries/lua-%LUA_RELEASE%_Win64_dllw6_lib.zip
       LUA_DIR: D:\Lua
+      # do not want \L to end up in pathdef.c and compiler complaining about unknown escape sequences \l
+      LUA_DIR_SLASH: D:/Lua
       # Python 2
       PYTHON_VER: 27
       PYTHON_VER_DOT: '2.7'
@@ -510,7 +512,7 @@ jobs:
             mingw32-make -f Make_ming.mak -j2 \
               FEATURES=${{ matrix.features }} \
               GUI=yes IME=yes ICONV=yes VIMDLL=yes \
-              DYNAMIC_LUA=yes LUA=${LUA_DIR} \
+              DYNAMIC_LUA=yes LUA=${LUA_DIR_SLASH} \
               DYNAMIC_PYTHON=yes PYTHON=${PYTHON_DIR} \
               DYNAMIC_PYTHON3=yes PYTHON3=${PYTHON3_DIR} \
               STATIC_STDCPLUS=yes COVERAGE=${{ matrix.coverage }}

src/version.c

@@ -746,6 +746,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    4856,
 /**/
     4855,
 /**/