gitweb.cgi: Create $git_temp if it doesn't exist
gitweb.cgi: Create $git_temp if it doesn't exist

Unless we'd done diffs, $git_temp doesn't exist and then
mime lookups fail.  Explicitly create it, if it doesn't
exist already.

Signed-off-by: Luben Tuikov <fc70afabee4d46c315ca5eabc5575472d236196f@yahoo.com>
Signed-off-by: Junio C Hamano <dc50d1021234060e53ec42a77d526afa2fe07479@cox.net>

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