(cherry picked from commit e72610a3)

(cherry picked from commit 8e05de17)

* Stop-gap for now. Ideally the logic would be in the respective places.

# Conflicts:
#	src/sdl/mixer_sound.c

# Conflicts:
#	src/sdl/mixer_sound.c

Merge branch 'music-cleanup' of https://git.magicalgirl.moe/STJr/SRB2Internal.git into music-cleanup

* I_GetMusicType() -> I_MusicType()
* Wrap MIDI volume hack in #ifdef _WIN32

* S_MusicInfo method to retrieve name, flags, and looping

* S_Init -> S_InitSfxChannels because it did mostly SFX anyway
* S_MusicPlaying, S_MusicPaused, S_MusicName, S_MusicExists new status methods
* I_MusicPlaying, I_MusicPaused

* In s_sound, they are merged to one method as well, but there are still two separate digvolume and seqvolume variables
* Simplified Dig/MidiMusicDisabled in s_sound
* Method reordering

* Revised S_PlayMusic arguments
* Now music plays again!

* Pause/ResumeSong remove handle argument
* LoadSong declare char *data argument
* Variable weirdness

This reverts commit 58fbb463.

# Conflicts:
#	src/android/i_sound.c
#	src/dummy/i_sound.c
#	src/win32/win_snd.c

This reverts commit b5c30958.

# Conflicts:
#	src/i_sound.h
#	src/s_sound.c
#	src/s_sound.h
#	src/sdl/mixer_sound.c

* Re-purpose I_LoadSong for digital music loading
* I_StartDigSong logic split between I_LoadSong and I_PlaySong
* Pause, Stop, and Unload routines are combined from Digi and MIDI
* music_lumpnum, music_data, music_handle from s_sound.c are gone

This reverts commit 8b46bce1.

* music_lumpnum, music_data, music_handle are gone
* Relevant interfaces I_PlaySong are transferred to I_StartDigSong

# Conflicts:
#	src/sdl12/i_cdmus.c
#	src/win32ce/win_cd.c

update XPM icon

See merge request !267

Change default sound volume

See merge request !238