Cygwin: regex: fix freeing g->charjump in low memory condition

computejumps() moves g->charjump to a position relativ to the value of
CHAR_MIN.  As such, g->charjump doesn't necessarily point to the address
actually allocated.  While regfree() takes that into account, the low
memory handling in regcomp_internal() doesn't.  Fix that by free'ing
the actually allocated address, as in regfree().

Signed-off-by: Corinna Vinschen <corinna@vinschen.de>

winsup/cygwin/regex/regcomp.c

@@ -336,7 +336,7 @@ regcomp_internal(regex_t * __restrict preg,
 		computejumps(p, g);
 		computematchjumps(p, g);
 		if(g->matchjump == NULL && g->charjump != NULL) {
-			free(g->charjump);
+			free(&g->charjump[CHAR_MIN]);
 			g->charjump = NULL;
 		}
 	}