emulators/ppsspp: add new port

PPSSPP is a PSP emulator written in C++. It translates PSP CPU
instructions directly into optimized x86, x64 and ARM machine code,
using JIT recompilers (dynarecs).

PPSSPP can thus run on quite low-spec hardware, including stronger
ARM-based phones and tablets, as long as there's OpenGL ES 2.0
support.

http://www.ppsspp.org/development.html

Requested by: RyanBram @ PCBSD forums
Motivated by: review D2608 (thus .ifdefs)