What changed in EDuke32, build by build

Clear GL depth buffer before drawing a frame in Polymost. This should fix the issue with skies in the Duke64 TC.

Revert "Polymost "use tile shades": don't confound shade and visibility." Temporarily add a r_usetileshades 2 to switch between Helixhorned and myself's ideas of how this should work.

Fix a weird problem where the arrow keys would sometimes send a shift keypress on Windows, manifesting in odd things like inconsistent turning speeds when using the keyboard, the grid helper lines showing up in Mapster32 when they weren't supposed to, etc. For some reason, an extra raw input keyboard event is generated with an out of bounds VKey value (0xFF) which must be filtered for proper operation. I wasn't able to find any official documentation regarding this but I did find it mentioned in a couple of random newsgroup/forum postings.

Unify glow and detail texture setup between polymost and mdsprite

Make the menus look the same in all rendering modes, because the LOADSCREEN tile looks like shit when any kind of palette-based shading is involved. So, now everyone gets the ugly metal looking MENUSCREEN.

Get rid of that old model occlusion checking hack I wrote for Polymost years ago. I actually didn't know this was still in EDuke32... it's one of the worst things I've ever written. :p

A bit more work on the Polymost shade table mode (r_usetileshades)

Add an experimental shading mode to Polymost for .art tiles, in which extra textures are allocated for each shade level based on the classic mode shade tables. Enable with r_usetileshades 1 (disabled by default). This uses a lot of memory and is still very WIP (a lot of the shading is completely wrong at this point).

Fix issue with Polymer checkbox in startup window, as reported at http://forums.duke4.net/topic/2961-paper-cuts-minor-bugs-and-annoyances/page__view__findpost__p__158208

Automatically execute mapname.cfg at map load time. This allows different maps in mods to have different rendering settings (shadescale, etc). This is not currently suitable for standalone user maps as there's no functionality to reset such cvars back to default at the next map load (so, if using this in a mod, every map needs to have a cfg).

Mask the seam that shows up when drawing the scuba HUD overlay in OpenGL by drawing SCUBAMASK 3 times... once at the left position + 1, and then at the proper left and right positions. It's definitely a hack, but at least it lives on the game side of things.

Fix changing the max refresh rate in EDuke32 (it was already working correctly in Mapster32).