[NEW PORT] games/libretro-fmsx: FMSX - MSX Emulator

This is a libretro core for fMSX, one of the oldest MSX1/2/2+ Computers emulators.

PR: 246120
Submitted by: menelkir@itroll.org
Approved by: tcberner (mentor)
Differential Revision: https://reviews.freebsd.org/D24865