qapi: Have each QAPI schema declare its name rule violations

qapi.py has a hardcoded white-list of type names that may violate the
rule on use of upper and lower case.  Add a new pragma directive
'name-case-whitelist', and use it to replace the hard-coded
white-list.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <1489582656-31133-7-git-send-email-armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
