PACKAGE/DEFCONFIG: create/add libretro-frodo pkg

[Apaczer]

Include COMMODORE 64 support via retroarch:

• add libretro-frodo pkg under packages/miyoo/retroarch

The gm2x shorcut should be auto-generated (if PR #189 merged), so no need to adding one

NOTES:
This is from https://github.com/Apaczer/frodo4/tree/libretro because (again) I might be adding savestate support in the future - this is "experimental" core, the benefit is better speed than standalone (despite sharing the same base CVS code from OE maintainer)

EDIT:
The "Keyboard emulation" here means emulate extra c64 keys via RetroPad (JOYPAD) binds, so generally you want this ON for solny playing on handheld (opposite to UAE4ALL where "Keyboard emulation" means emulate amiga keys via RetroKeyboard, so OFF in same scenario) - might think about changing naming

[Apaczer]

I have more ideas, how to improve it over existing code (add dynamic Pallete change, emulate extra joy buttons 2-3), but should be good for now.

Moreover some d64 apps don't work despite them running just fine in Frodo2Go (almost the same code, just pure SDL backend), good example: 64 Doctor