Teach commit parser about author/committer email + timestamp

We want all four of these when showing a commit, so save them in the
commitinfo struct.

Btw: There's probably no good reason to save committer timestamp since
it's already available in commit->date. But it doesn't hurt us either,
and it makes the parser look more complete, so we just do it.

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

cgit.h

@@ -18,7 +18,11 @@ struct cacheitem {
 struct commitinfo {
 	struct commit *commit;
 	char *author;
+	char *author_email;
+	unsigned long author_date;
 	char *committer;
+	char *committer_email;
+	unsigned long committer_date;
 	char *subject;
 	char *msg;
 };