(multiplatform) selectable aspect ratio drop-down list

[eugene-s-nesdev]

Accordings to pull-request for libretro and aspect ratio change depending region: https://github.com/rdanbrook/nestopia/pull/201 https://github.com/rdanbrook/nestopia/commit/cd13ccbb3096b3ede21c895ce18578f13926cfbe

Can you add drop-down list to multiplatform port, which contain:

auto ntsc pal 4:3

aspect ratios. Auto mode will set NTSC aspect ratio (8:7) for NTSC/Famicom and PAL aspect ratio (1.3862:1) for PAL/Dendy, as well, as it done by arakerlu (#201)

Option "4:3" is removed on libretro because I don't see any need for it and seems rather arbitrary and redundant - if you want to use it you can set it in frontend/Retroarch.

4:3 (or 5:4 PAR) is useful too, don't remove it please, just make it selectable. frontend/Retroarch aspect ratio better set to "core provided" all the time, i guess. User can switch cores between nestopia and gambatte, for example. Not comfortable to switch AR every time you change core.