parsing.c: be prepared for unexpected content in commit/tag objects

When parsing commits and tags cgit made too many assumptions about the
formatting of said objects. This patch tries to make the code be more
prepared to handle 'malformed' objects.

Signed-off-by: Lars Hjemli <hjemli@gmail.com>

cgit.h

@@ -85,7 +85,7 @@ struct commitinfo {
 struct taginfo {
 	char *tagger;
 	char *tagger_email;
-	int tagger_date;
+	unsigned long tagger_date;
 	char *msg;
 };