Type names should be CamelCase.  Enforce this.  The only offenders are
in tests/.  Fix them.  Add test type-case to cover the new error.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <20210323094025.3569441-15-armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
[Regexp simplified, new test made more robust]