Emulated CD drive Speed support

[scentgames]

Mednafen got a CD Speed option on its PCE core with libretro, which enable to set the speed of the emulated CD drive and solve the issue of some Cutscene freezes/goes black in the CD games(e.g. Popful mail).
Love the emulator, please consider it. :)

[drhelius]

Popful Mail issues are fixed