Fix a comparison bug in diff-delta.c

(1 << i) < hspace is compared in the `int` space rather that in the
unsigned one.  the result will be wrong if hspace is between 0x40000000
and 0x80000000.

Signed-off-by: Pierre Habouzit <madcoder@debian.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>

diff-delta.c

@@ -152,7 +152,7 @@ struct delta_index * create_delta_index(const void *buf, unsigned long bufsize)
 	   initialization in create_delta(). */
 	entries = (bufsize - 1)  / RABIN_WINDOW;
 	hsize = entries / 4;
-	for (i = 4; (1 << i) < hsize && i < 31; i++);
+	for (i = 4; (1u << i) < hsize && i < 31; i++);
 	hsize = 1 << i;
 	hmask = hsize - 1;