gitweb.perl - Optionally send archives as .zip files

gitweb.perl - Optionally send archives as .zip files

git-archive already knows how to generate an archive as a tar or a zip
file, but gitweb did not. zip archvies are much more usable in a Windows
environment due to native support and this patch allows a site admin the
option to deliver zip rather than tar files. The selection is done by
inserting

    $feature{'snapshot'}{'default'} = ['x-zip', 'zip', ''];

in gitweb_config.perl.

Tar files remain the default option.

Signed-off-by: Mark Levedahl <mdl123@verizon.net>
Acked-by: Petr Baudis <pasky@suse.cz>
Signed-off-by: Junio C Hamano <junkio@cox.net>