(cherry picked from commit 9fb9386f84b3739fe765a78bcb9683eb7e98bc36)

* 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

(cherry picked from commit 701cc5a7dd1dfead87a42ec7558c9fa6a1deb193)

(cherry picked from commit 14b393ab16736bb44dab6fd4a90b7bdd8ff782e0)

* Revised S_PlayMusic arguments
* Now music plays again!

(cherry picked from commit 55f3803e4b9f8104c90cc6c769d54121e5bac0b8)

(cherry picked from commit 9a5fc5f66a31baf713c6f32f7a696b933da6907b)

Colormap code cleanup

See merge request STJr/SRB2!275

R_CreateColormap2 and R_MakeColormaps have been made obsolete, it's just R_CreateColormap now, like it used to be!

With that, I moved R_CreateColormap2's exclusive software colormap malloc code to R_CreateColormap, and merged the two software-only blocks of code into one. I also disabled any unneeded variables and fixed a preprocessor-related goofup

Fix for HOM removal in non-green resolutions

See merge request STJr/SRB2!273

Yo Screen So Wide y Is Invalid

See merge request STJr/SRB2!271

v_video Killed The r_radio Star

See merge request STJr/SRB2!270

Zalloc Potter and the Death-Free Hallows

See merge request STJr/SRB2!269

Lighting fixes? Plane and simple!

See merge request STJr/SRB2!268

Introduce a temporary measure to enable the old stuff, minus one of the most obviously terrible bugbears of yesteryear. Let it be known that any downstream poirt will almost certainly toggle this ASAP.

Clean up a bunch of v_video.c functions that previously exhibited unfortunate side effects when run in non-green resolutions.

* V_DrawFixedPatch and ilk:
	* Change the offset of V_FLIP so it's not one screen-pixel off where its non-flipped sprite would have started being drawn from.
	* Write to x and y as well as desttop so that anti-screen-overflow checks later in the function behave properly with non-green resolutions.

* V_DrawFill:
	* Reduce number of operations performed upon `c`.

* V_DrawString and ilk:
	* Offset the left and right boundary checks in non-green resolutions such that you can actually draw stuff to the left of basevid screen x coordinate 0.

* Stop orphaning their memory. They ARE PU_LEVEL, so they'll disappear eventually, but, like... it's not good memory management practice to just *orphan* them when you're literally never going to do anything with them ever again. Y'know?
* Make ghosts spawn properly on slopes.

* Fix that thing where ALL transparent FOF planes were continuously fullbright unless encased in a fog which disables sprite fullbrightness, which was long-hated by many people in the community!
	* For backwards compatibility, setting flag 1 in that fog field (which is probably the most common "in-the-wild" usage of this feature) will continue to make objects un-fullbright.
	* For situations where you desperately want the behaviour to be enabled, you can apply fog flag 2.
* Change the fadestart and fadeend range in which colormaps are generated.
	* The problem HERE was that the darkest light level reached by generated colormaps was actually slightly brighter than the darkest level reached by normal colormaps.
	* The typo I fixed does have SOME basis in fact - standard colormap lumps are 34 (33 in 0-indexing) long rather than 32 (31), but whoever wrote this didn't realise that the code for generating them didn't do it DooM style, just bright-to-dark with no extras on the end...

update XPM icon

See merge request STJr/SRB2!267

Change default sound volume

See merge request STJr/SRB2!238

SDL Mixer fixes

Closes #31

See merge request STJr/SRB2!260

Fix white being treated as transparent.

See merge request STJr/SRB2!266

Woops! All trans

See merge request !265

Transparency? I hardly knew 'er!

See merge request STJr/SRB2!264

Change the order of operations when applying transparency and colormap such that colormap isn't applied to the screen pixel twice (or, in the case of R_DrawTranslatedTranslucentColumn_8, thrice).

Please note I haven't touched the ASM equivalent, given as it's not actually used.

Password fix hotfix

See merge request STJr/SRB2!261

Quick fix for LJ's password fix: don't check if password is set until we've confirmed that the receiving player is the server!

GME low volume fix

See merge request STJr/SRB2!248

Fix pausing on gme

See merge request STJr/SRB2!251