renamed and documented the core GLimp functions
moved the memset calls out of GLimp_Shutdown
dealing with anisotropic filtering properly and fixed the cvar's range and help
platform extension loading is done through Sys_GL_LoadExtensions
throwing fatal errors is done by the renderer exclusively
removed QGL_Init and QGL_Shutdown
cleaned up glconfig_t
filling up the unused glConfig fields in the renderer for old mods
