mint-arena: Rename auto resolution's aspect (1.33:1 -> 4:3)

It was already done for regular resolutions.
mint-arena: Add system calls for checking if numlock/capslock is enabled

This was previously done using trap_Key_IsDown(), which doesn't work after changing to SDL2 (on linux at least?). Plus Explicit API seems better.
Merge remote-tracking branch 'mint-arena/master'