OpenGL2: Remove AGEN_FRESNEL(superceded by cubemap patch), and some small fixes and optimizations.
OpenGL2: default to RGBM lightmap, and add r_floatLightmap for old behaviour.
Revert "5097 - Menu corrupted on start (on IRIX)"

Calling glClear( any bits ) in GL_SetDefaultState makes connect screen black using the proprietary NVidia driver on Windows and GNU/Linux.

This reverts commit 92573270de98a20cd78842bd2043cfe07bc5b2e1.
Merge remote-tracking branch 'ioquake3/master'

Conflicts:
	code/renderergl2/tr_bsp.c