Deprecate FcName(Un)RegisterObjectTypes / FcName(Un)RegisterConstants

Deprecate FcName(Un)RegisterObjectTypes / FcName(Un)RegisterConstants

These never worked as intended.  The problem is, if Fontconfig tries to
read config files when these new types / constants are not registered,
it errs.  As a result, no defined types / constants are usable from
config files.  Which makes these really useless.  Xft was the only user
of this API and even there it's not really used.  Just kill it.

One inch closer to thread-safety since we can fix the object-type hash
table at compile time.