gitweb: make the supported snapshot formats array global
gitweb: make the supported snapshot formats array global

The array of supported snapshot format is used and defined (with two
different names) in two routines, one of which (format_snapshot_links)
is often called multiple times per page.

Simplify code and speed up page generation by making the array global.

Signed-off-by: Giuseppe Bilotta <6010d7f2c049984f25cd19568d4ace2cc46b0817@gmail.com>
Signed-off-by: Junio C Hamano <a6723cc3f76163bf7adb636a73ac3b0ceb3e6b9b@pobox.com>

destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git