Correct C FixedMul() off-by-one errors

See merge request STJr/SRB2!245

F12 fix

See merge request STJr/SRB2!250

OpenGL: Map Specific Palette Fix

See merge request !247

OpenGL: Very large map rendering issue fixed

See merge request STJr/SRB2!249

Fix console typo

See merge request STJr/SRB2!246

OpenGL: Fix FF_FULLBRIGHT not working in sectors with multiple light levels

See merge request STJr/SRB2!244

This should hopefully kill the F12 getting stuck issue once and for all.

Move old fix for too large maps having rendering issues from R_CheckBBox to OpenGL's HWR_CheckBBox
From what I know, this effects at least Aerial Garden and Seraphic Skylands

The FixedMul() C implementation would produce off by one results,
causing constant desyncs on 64 bit builds and builds without an
ASM implementation of the function.

This is fixed by shifting instead of dividing, possibly avoiding
rounding errors.

This makes OpenGL stop using a specific function that doesn't really do anything for it anymore. It looks like it was used for a hack that would change the colour of polygons for the flashpal equivalent in DOOM.
I made it so ST_DoPaletteStuff doesn't set the flashpal in OpenGL as it already does its own hacky overlay and doing that would cause all the textures to be flushed more mid-level, it could be enabled for more correct flashpals, but they still wouldn't effect fog or lighting.
This means the palette will be set when going to the title screen, and twice when starting a map, (causing the OpenGL cached textures to also be flushed at those times)

Don't init the sound system on dedicated servers

See merge request STJr/SRB2!225

Fixed "invalid pointer" error when passing "" to Command_connect().

See merge request !234

Removed contradictory `-connect` check

See merge request STJr/SRB2!236

Rewrite of d_netfil.c's findfile

See merge request STJr/SRB2!240

Dedicated debug hotfix

See merge request STJr/SRB2!239

Movie mode: special stage intro fade recording fix

See merge request STJr/SRB2!229

Rewrote findfile to store whether any of the three paths searched had a bad MD5 rather than just simply being not there.

This means that, if the three paths are not the same, you should be able to tell if at least one of them has a file that just had a bad MD5. Most relevant for Linux peeps I expect.

Note: Untested as of writing

Opengl Quick Fixes

See merge request STJr/SRB2!237

I wasn't aware of the cvar, this should do for now since I don't believe any maps use these software tricks, probably an old leftover from DOOM.

I don't fully understand this, but it's what software does and it fixes the issue of the lighting in DSZ3. Also don't need the extra call to R_Prep3DFloors.

I don't think it does anything for us anymore, and might even break things with slopes.
Someone let me know if I'm wrong and am breaking things horribly here.

Transformation based on screen space would make sense if we didn't want anything in the world to effect the sprites.
This should allow sprite splitting and sorting of sprites with level geometry easier.
stransform is no longer needed.

Solid walls *can* be cut
Fix issues with water and fog FOFs not cutting each other out correctly
Fix Fog colourmap and lighting setting that is done here.
Remove HWR_SplitFog

There is currently a bug with FF_DOUBLESHADOW (that also exists in software) but has a larger impact here. When 2 FF_DOUBLESHADOW lights are directly stacked on each other the bottom one has its height set incorrectly. This causes all the Fog in the timed gravity flipping section of ERZ2 to be drawn and it looks really bad.

This reverts commit 121fcd83.

The reason I am reverting this is because the last commit actually fixes the *old* screenshot functionality, as the screen is being drawn back onto the buffer after they're swapped in the "real" size. Meaning the old function actually works perfectly fine now.

Only applies when the monitor aspect ratio is different to the game's aspect ratio.

My IDE doesn't seem to like Vada's name.