25 is woefully small for the number of packages many searches can
return, and with 28000+ packages in AUR, it makes sense to show a lot
more per page by default.

The new choices of (50, 100, 250) happen to match those from the main
site.

Signed-off-by: Dan McGee <dan@archlinux.org>
Signed-off-by: Lukas Fleischer <archlinux@cryptocrack.de>