This is all in unused/unnecessary/leftover code, but the code wouldn't
build without Xlib headers on the system, which was forcing the Mac builds
to install xquartz.
This also removes renderer/SoftwareOpenGL*, which was _not_ a
software-rendered OpenGL, but just an older version of the same code that's
in HardwareOpenGL.cpp--old enough to still talk to glX directly, which is
what caught my attention.