branches/zip: trx0sys.ic: Correct a typo in a comment.

include/trx0sys.ic

@@ -19,7 +19,7 @@ typedef byte	trx_sysf_rseg_t;
 #define	TRX_SYS_RSEG_SPACE	0	/* space where the the segment
 					header is placed; starting with
 					MySQL/InnoDB 5.1.7, this is
-					UNIV_UNDEFINED if the slot is unused */
+					ULINT_UNDEFINED for unused slots */
 #define	TRX_SYS_RSEG_PAGE_NO	4	/*  page number where the the segment
 					header is placed; this is FIL_NULL
 					if the slot is unused */