patch 8.0.0554: toupper and tolower don't work properly for Turkish

Problem:    Toupper and tolower don't work properly for Turkish when 'casemap'
            contains "keepascii". (Bjorn Linse)
Solution:   When 'casemap' contains "keepascii" use ASCII toupper/tolower.

src/charset.c

@@ -1733,6 +1733,8 @@ vim_toupper(int c)
 	if (enc_latin1like)
 	    return latin1upper[c];
     }
+    if (c < 0x80 && (cmp_flags & CMP_KEEPASCII))
+	return TOUPPER_ASC(c);
     return TOUPPER_LOC(c);
 }
 
@@ -1757,6 +1759,8 @@ vim_tolower(int c)
 	if (enc_latin1like)
 	    return latin1lower[c];
     }
+    if (c < 0x80 && (cmp_flags & CMP_KEEPASCII))
+	return TOLOWER_ASC(c);
     return TOLOWER_LOC(c);
 }
 #endif

src/testdir/test_normal.vim

@@ -1619,6 +1619,17 @@ fun! Test_normal30_changecase()
       call assert_equal("i\u0131", getline(1))
       call assert_equal("i\u0131", tolower("iI"))
 
+      set casemap&
+      call setline(1, 'iI')
+      1normal gUU
+      call assert_equal("II", getline(1))
+      call assert_equal("II", toupper("iI"))
+
+      call setline(1, 'iI')
+      1normal guu
+      call assert_equal("ii", getline(1))
+      call assert_equal("ii", tolower("iI"))
+
       lang en_US.UTF-8
     catch /E197:/
       " can't use Turkish locale

src/version.c

@@ -764,6 +764,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    554,
 /**/
     553,
 /**/