There are three differences between the two (as verified by sort, sed,
uniq, and diff):

- enum.spec includes GLES extension enums (since it's used for
  maintaining uniqueness of enums in the registry), which we want to
  include for cross-API compatibility.
- enum.spec includes some entries for known GL versions and GL extensions.
- enumext.spec has a few more synonyms for enums (since it's the
  file used for generating the official glext.h for desktop).

This change only introduces new #define lines to generated-dispatch.h.

v2: Make the statement about "only introduces new #define lines"
    actually true by continuing to emit based on the categories we
    collected during parsing, except with them defined to '1' instead
    of '', to match actual glext definitions and what gets
    autogenerated from enum.ext.

Reviewed-by: Chad Versace <chad.versace@linux.intel.com>