ctype.c: protect tiny C preprocessor constants

Some platforms contaminate the preprocessor token namespace with their own
definition of SS without being asked.  Avoid getting hit by redefinition
warning messages by explicitly undef SS, AA and DD shorthand we use in this
table definition.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

ctype.c

@@ -5,6 +5,11 @@
  */
 #include "cache.h"
 
+/* Just so that no insane platform contaminate namespace with these symbols */
+#undef SS
+#undef AA
+#undef DD
+
 #define SS GIT_SPACE
 #define AA GIT_ALPHA
 #define DD GIT_DIGIT