* 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 STJr/SRB2!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

This should prevent I_FreeSfx making a mess of things later, hopefully.

OpenGL: FOF walls + Lower unpegged

See merge request STJr/SRB2!258

OpenGL HWR_ProjectSprite fix

See merge request STJr/SRB2!255

More helpful error messages

See merge request STJr/SRB2!243

Smoother MD2 interpolation

See merge request !224

Fixed MD2 models not loading correctly on Linux

Lua exploit fix

See merge request STJr/SRB2!259

Disable admin password by default

Minor net command fixes