apply: handle patches with funny filename and colon in timezone

Some patches have a timezone formatted like '-08:00' instead of
'-0800' in their ---/+++ lines (e.g. http://lwn.net/Articles/131729/

).
Take this into account when searching for the start of the timezone
(which is the end of the filename).

This does not actually affect the outcome of patching unless (1) a
file being patched has a non-' ' whitespace character (e.g., tab) in
its filename, or (2) the patch is whitespace-damaged, so the tab
between filename and timestamp has been replaced with spaces.

Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>