patch 8.0.0452: some macros are in lower case

Problem:    Some macros are in lower case.
Solution:   Make a few more macros upper case.
diff --git a/src/userfunc.c b/src/userfunc.c
index 1bf028f..07cc47f 100644
--- a/src/userfunc.c
+++ b/src/userfunc.c
@@ -2104,7 +2104,7 @@
 	else
 	{
 	    /* skip ':' and blanks*/
-	    for (p = theline; vim_iswhite(*p) || *p == ':'; ++p)
+	    for (p = theline; VIM_ISWHITE(*p) || *p == ':'; ++p)
 		;
 
 	    /* Check for "endfunction". */