Merge branch 'z_osx_clean' of https://github.com/alexey-lysiuk/gzdoom into gz_osx
- fixed: inverted rendering for fuzzy things with light powerup was switched off due to change of render style.
- fixed: MODELDEF's FrameIndex command was case sensitive.
- fixed weapon drawing rules to account for the death camera.
- fixed memory leak: The sector links for dynamic lights were never freed.
- fixed: The texture mode implied by render style did not work for models.
- fixed: The PolyBSPs weren't fully initialized. Some GZDoom-only fields in the segs were skipped.
 - we don't really need a bBrightmap in a texture. All it did was duplicate some functionality of bMasked.

- renamed bBrightmapDisablesFullbright flag.
- now that we don't have to care anymore about SVN-related merging problems, let's save the 3 global variables of the GL renderer unconditionally, even if the software renderer is running.
Fixed compilation after all those cherry picks
- obsolete .xib resource
Removed OpenGL 2.1 requirement

OpenGL 2.0 is still needed in order to run GZDoom
Merge branch 'gz_osx' of https://github.com/alexey-lysiuk/gzdoom into osx