Libretro wrapper for bsnes-mercury accuracy core

 This wrapper makes bsnes-mercury accuracy core API compatible with libretro,
 thus allowing its use with libretro frontends, such as RetroArch.
 .
 This core is enabled to emulate only SNES hardware and its subsystems (from
 the command line only), like Super Game Boy, Satellaview and Sufami Turbo.
 .
 bsnes-mercury is a fork of higan, aiming to restore some useful features that
 have been removed, as well as improving performance a bit. Maximum accuracy is
 still uncompromisable; anything that affects accuracy is optional and off by
 default. The name is because metals are shiny, like the accuracy promises of
 bsnes, and mercury is the fastest metal.
 .
 This package comes with the bsnes-mercury accuracy core, which runs 100% of
 SNES games, with perfect emulation of the console. It requires high CPU usage.