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/macros.h b/src/macros.h
index 97e7e83..8ebc8ce 100644
--- a/src/macros.h
+++ b/src/macros.h
@@ -46,6 +46,12 @@
 #define LTOREQ_POS(a, b) (LT_POS(a, b) || EQUAL_POS(a, b))
 
 /*
+ * VIM_ISWHITE() is used for "^" and the like. It differs from isspace()
+ * because it doesn't include <CR> and <LF> and the like.
+ */
+#define VIM_ISWHITE(x)	((x) == ' ' || (x) == '\t')
+
+/*
  * LINEEMPTY() - return TRUE if the line is empty
  */
 #define LINEEMPTY(p) (*ml_get(p) == NUL)