Replace isupper with a macro in msvc

src/parse.y

@@ -42,6 +42,10 @@ static void backref_error(parser_state *p, node *n);
 #define isascii(c) (((c) & ~0x7f) == 0)
 #endif
 
+#ifdef _MSC_VER
+#define isupper(c) ((c) >= 'A' && (c) <= 'Z')
+#endif
+
 #define identchar(c) (isalnum(c) || (c) == '_' || !isascii(c))
 
 typedef unsigned int stack_type;