More futureproofing hypotheticals

If you set COLNO larger than BUFSZ, few places cause a buffer overrun.
Add a new buffer size definition, COLBUFSZ, which is the larger of
COLNO and BUFSZ, used in places that care about a screen-wide string.

include/global.h

@@ -370,6 +370,13 @@ struct savefile_info {
 #define TBUFSZ 300 /* g.toplines[] buffer max msg: 3 81char names */
 /* plus longest prefix plus a few extra words */
 
+/* COLBUFSZ is the larger of BUFSZ and COLNO */
+#if BUFSZ > COLNO
+#define COLBUFSZ BUFSZ
+#else
+#define COLBUFSZ COLNO
+#endif
+
 #define PL_NSIZ 32 /* name of player, ghost, shopkeeper */
 #define PL_CSIZ 32 /* sizeof pl_character */
 #define PL_FSIZ 32 /* fruit name */