Add screenshot taking

[Epicpkmn11]

This (tries to) add screenshot taking, at the moment it's rather broken as I'm not able to compile GBARunner2 myself to test and I'm not familiar with it's codebase, but I'll try fix it up soon.

The icon is the Photo Camera from Google Fonts, as GBARunner2 has a material design style so figured that's probably where the icons are from? It's also a bit of a bad scale down at the moment though so I'll probably try clean that up too.

• Closes [Enhancement] Screenshot Function in GBArunner2 #209

Update: It works now!

[Epicpkmn11]

Rebased onto feature/dsp-audio as Azure works on this branch. I can rebase to something else if wanted when done, but this way I'm actually able to test. Sorry if I'm a bit spammier on commits than usual, I can't exactly test without committing.

[Epicpkmn11]

Sorry about all the force pushing, Azure was my only method of testing and I wanted to keep the commits somewhat clean.

It works now though! The file naming could almost certainly be done better, however I've had a very hard time since GBARunner2 doesn't seem to like arrays or memcpy or a bunch of other things, so this is the best I've been able to do. It'll save screenshots to sd:/_gba/screenshots/screenshot-####.bmp where #### is a zero padded number.

Tested on DSi and DS, works both with and without center & mask on.

Edit: Sometimes the first 48 lines are being missed, I've never seen it happen in MK:SC, but it's pretty common in LEGO Star Wars: The Video Game. This doesn't seem to be a new bug though as it's also missing on the copy while in the menu, even on master.