Enable --escape-exit for all relevant (e.g. non-mobile) platforms. 

Whoops, branch name should've been escapeExitOption. Whatever.

It makes PPSSPP more front-end friendly by letting escape (and whatever else is bound to Pause) quit the emu. Its name makes more sense now, and *nix users can join in the fun.

The option will stay named as escape-exit though, since the primary audience likely uses escape anyway.