qapi: Clean up member name case checking

qapi: Clean up member name case checking

QAPISchemaMember.check_clash() checks for member names that map to the
same c_name().  Takes care of rejecting duplicate names.

It also checks a naming rule: no uppercase in member names.  That's a
rather odd place to do it.  Enforcing naming rules is
check_name_str()'s job.

qapi-code-gen.txt specifies the name case rule applies to the name as
it appears in the schema.  check_clash() checks c_name(name) instead.
No difference, as c_name() leaves alone case, but unclean.

Move the name case check into check_name_str(), less the c_name().
New argument @permit_upper suppresses it.  Pass permit_upper=True for
definitions (which are not members), and when the member's owner is
whitelisted with pragma name-case-whitelist.

Bonus: name-case-whitelist now applies to a union's inline base, too.
Update qapi/qapi-schema.json pragma to whitelist union CpuInfo instead
of CpuInfo's implicit base type's name q_obj_CpuInfo-base.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20190927134639.4284-6-armbru@redhat.com>