glx: Don't use glapitable.h at all

glx: Don't use glapitable.h at all

When --enable-shared-glapi is used, all non-ABI entries in the table are
lies.  Avoiding the use of glapitable.h avoids the lies.  The only
entries used in this code are entries that are ABI.  For these, the ABI
offset can be used directly.

Since this code is in src/glx, it can't use src/mesa/main/dispatch.h to
get the pretty names for these offsets.

Signed-off-by: Ian Romanick <ian.d.romanick@intel.com>