Merge pull request #15 from libretro/master

Latest libretro updates
[MD] added support for recently dumped game "Gunfight 3-in-1" (unlicensed)
[Core/YM2612] fixed configurable DAC resolution support
[Core/General] minor emulation fixes
[Core/SCD]
.fixed SEEK command emulation (Lunar the Silver Star freeze regression)
.added .OGG files support for CD audio tracks (use same naming convention as
.WAV files, cf. README.pdf)

[Win32]
removed win32/SDL port makefile to prevent stupid websites like EmuCR from
compiling & distributing it (for the last time, it's a buggy, unstable &
incomplete port which is not meant to be used for anything but debugging)
[Core/Sound]
. added optional MONO output mode
. improved Low-Pass filter

[Gamecube/Wii]
. added configurable deflickering filter (normally enabled by default)
. various improvement & bugfixes
[libretro] fixed compilation issues & removed unused code
rearranged core & back-end specific code
rearranged core & back-end specific code (part 2)
[libtremor] fixed C89 incompatibilities
updated headers of modified files
[Core/SCD] improved .cue file parsing