SDL_Mixer_X Engine Upgrades

Upgrades SDL_Mixer_X to Version 2.6.0.

To compensate with this upgrade, most SDL_Mixer_X and mixer_sound.c functions have been updated, allowing them to have more capabilities and features.

• General optimizations to functions have been added.
• CMake can now find and compile with SDL_Mixer_X libraries.

Additional DLLs have also been added and replaced.

• libfluidlite.dll now replaces libfluidsynth-2.dll.
• libwinpthread-1.dll and libstdc++-6.dll have been added.
• libgcc_s_sjlj-1.dll has been removed.
• x86_64 systems:
  • libgcc_s_seh-1.dll has been added.
• i686 systems:
  • libgcc_s_dw2-1.dll has been added.
• The Timidity system has been fairly overhauled.

FUNCTIONS:
Revamped functions include:

• S_SpeedMusic
  • Now works with OGG files and more formats.
  • Can't be used as a boolean function anymore. Instead, the new functions take its place in that regard.
• S_SetInternalMusicVolume
  • Minorly modified, just stores internal volume values in a variable, allowing for the internal volume to be grabbed and returned.

New functions include:

• float S_GetSpeedMusic
• void S_PitchMusic
  • NOTE: Only works with OpenMPT, GME, and MIDI, due to SDL_Mixer-X restrictions.
• float S_GetPitchMusic
• INT32 S_GetInternalMusicVolume
• void S_SetInternalSfxVolume
• INT32 S_GetInternalSfxVolume

All of these new functions can now be used with BLUA as well.

HOW THE NEW IMPLEMENTATIONS FUNCTION IN-GAME:

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