Fix warning about bitfield in struct ref

cache.h:503: warning: type of bit-field 'force' is a GCC extension
cache.h:504: warning: type of bit-field 'merge' is a GCC extension
cache.h:505: warning: type of bit-field 'nonfastforward' is a GCC extension
cache.h:506: warning: type of bit-field 'deletion' is a GCC extension

So we change it to an 'unsigned int' which is not a GCC extension.

Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

cache.h

@@ -493,10 +493,10 @@ struct ref {
 	struct ref *next;
 	unsigned char old_sha1[20];
 	unsigned char new_sha1[20];
-	unsigned char force : 1;
-	unsigned char merge : 1;
-	unsigned char nonfastforward : 1;
-	unsigned char deletion : 1;
+	unsigned int force:1,
+		merge:1,
+		nonfastforward:1,
+		deletion:1;
 	enum {
 		REF_STATUS_NONE = 0,
 		REF_STATUS_OK,