Init volume in audio panel.

Otherwise, the volume slider had to be "touched" first before the actual
volume was in sync with the displayed value.
Improved ROTT GFX support.

Translucent masked textures seem to work now.
Only save modified texture definition lumps.

Don't overwrite unmodified texture definition lumps since people might
want to preserve TEXTURES comments.
Removed a bunch of wxWidgets 2.9.x baggage.

Some of which were broken when using wxWidgets 3.0.0 because suddenly
wxMINOR_VERSION and wxRELEASE_NUMBER were no longer greater than
whatever value was tested.
ZDoom mapinfo fix
Partial scaling support

Texture editor now handles old HIRESTEX-style "define" keyword.
Scaled flats are now handled by MapRenderer2D.
Scaled flats and textures are now handled by MapRenderer3D.
Hi-res textures are now actually displayed in the MapTextureBrowser.
Additionally, MapTextureBrowser now also subcategorizes by archive.
Made usage count case-insensitive.

Maybe the issue should instead be addressed upstream by forcing texture
names to be upper-case?
Merge pull request #68 from Gaerzi/master

Sync with my fork.