Seperate glX from HAVE_OPENGL, for platforms that have both an X server and a more official way to do OpenGL, explicitly check for glX on Mac OS X, and use SDL_LoadObject for platforms that have glX but don't have dlopen().

## Makefile.am for the Dreamcast cdrom driver for SDL

noinst_LTLIBRARIES = libcdrom_dc.la
libcdrom_dc_la_SOURCES = $(SRCS)

# The SDL cdrom driver sources
SRCS = SDL_syscdrom.c