Split ogl_get_verinfo() into ogl_tune_for_current() and
ogl_extensions_init(), and consolidate all the OpenGL extension handling
into ogl_extensions.cpp. Unify the code paths for texture anisotropy and
GPU synchronization for OpenGL and OpenGL ES.
Currently, our renderer only uses GLES 1.0, so no real world implementation
will support sync objects for such an old context, but the logic is valid,
and this way, the GLES specific code paths are reduced.
This patch also fixes an issue where the old ogl_get_verinfo() did modify
the texture filtering mode if no anisotropic filter was available. This
was some leftover from the time when the anisotropic filter was a just
a specific CGameConfig.TexFilt mode, and not a separate, orthogonal setting
CGameCfg.TexAnisotropy that it is now.
551570d29b