qapi: Document flaws in checking of names 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>