The current GetVideoMode() function stops at the first mode which has any
dimensions smaller than the one asked, and gives the previous in the list.

If I ask 336x224 with this list:
768x480 768x240 640x400 640x200 384x480 384x240 320x400 320x200
SDL will give me 640x400, because 640x200 as height smaller than what I
asked.

However the best mode is the smaller which has both dimensions bigger
than the one asked (384x240 in my example).

This patch fixes this, plus it does not rely on a sorted video mode list.

--HG--
extra : convert_revision : svn%3Ac70aab31-4412-0410-b14c-859654838e24/trunk%401077