We don't actually enforce our "other than downstream extensions [...],
all names should begin with a letter" rule. Add a FIXME.
We should reject names that differ only in '_' vs. '.' vs. '-',
because they're liable to clash in generated C. Add a FIXME.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>