Allow 'S' and 'L' keys to be mappable to the joypad (in the Controls menu)

[zzedmore]

Could you add the 'S' and 'L' keys to be mappable to the joypad in the Controls menu please ? This allows games like the Pajama Sam series to (S)ave and (L)oad the game ! We just played through a chunk of the game only to find out we couldn't save without a keyboard.

There are a select few keys that are available to map in the Controls menu but not 'S' and 'L'.

[spleen1981]

This could be solved using virtual keyboard available in ScummVM mainline libretro core, included in current Lakka master.