Import savegame thumbnail crash fix(r1279-r1280)

r1280 | svkaiser | 2014-03-01 20:07:37 -0800 (Sat, 01 Mar 2014)

+ Don't try to do any stupid cropping for widescreen resolutions when
saving out thumbnails

r1279 | svkaiser | 2014-03-01 20:07:04 -0800 (Sat, 01 Mar 2014)

+ Avoid using memcpy in GL_GetScreenBuffer