Added a new texture creation flag for specifying the desired texture format. The new flag chooses a non-alpha channel texture format. This will save some texture memory (one fourth for 32bit textures).
Fixed another COpenGL render state bug.
Fixed several color conversion methods.

git-svn-id: svn://svn.code.sf.net/p/irrlicht/code/trunk@801 dfc29bdd-3216-0410-991c-e03cc46cb475