Enabled GL_EXT_secondary_color. Fixed a bunch of typos in the dlist.c

Enabled GL_EXT_secondary_color.  Fixed a bunch of typos in the dlist.c
and state.c file for plugging those functions into the dispatch table.
Don't use Mesa 3.5 for DRI until SGI approves the new dispatch offsets.
Commented-out references to ctx->FogMode and VB->Specular in FX driver.
Minor clean-up in extensions.c
Removed unused prototype in fog.h