dix: Unexport various implementation details

dix/colormap.c

dix/dispatch.c

dix/dixfonts.c

dix/enterleave.c

dix/enterleave.h

dix/main.c

hw/xfree86/sdksyms.sh

include/Makefile.am

include/colormap.h

include/dixfont.h

include/dixstruct.h

include/swaprep.h

include/swapreq.h

mi/miglblt.c

miext/damage/damage.c

os/utils.c