Log message:
libretro-*: Support Darwin by cargo-culting SOEXT. Remove bsdtar hack.

Log message:
libretro-bsnes-mercury{,-accuracy,-performance}: add version 20180803

Libretro is a simple but powerful development interface that allows for
the easy creation of emulators, games and multimedia applications that
can plug straight into any libretro-compatible frontend. This development
interface is open to others so that they can run these pluggable emulator
and game cores also in their own programs or devices.

bsnes/higan is a Super Nintendo Entertainment System / Super Famicom
video game system emulator that aims to document SNES/SFC hardware with
an extremely high degree of accuracy without compromise or optimisation.

bsnes-mercury is a fork of bsnes/higan aiming to restore some useful
features that have been removed, as well as improving performance
slightly. Maximum accuracy is still uncompromisable; anything that
affects accuracy is optional and off by default.

As such, it has quite high system requirements. For a SNES/SFC libretro
core that balances performance and accuracy to an acceptable level for
99% of games, consider using a snes9x core.

Three profiles are available: Performance, Balanced, and Accuracy.
Balanced is recommended for modern PCs. Use Accuracy for extreme cases
of hardware spec abuse (e.g. the game A.S.P. Air Strike Patrol).