QAPISchemaModularCVisitor._begin_system_module() is actually just for
the builtin module. Rename it to ._begin_builtin_module() and drop
its useless @name parameter.
Clarify conditionals in visit_module to make this clear.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: John Snow <jsnow@redhat.com>
Message-Id: <20210201193747.2169670-7-jsnow@redhat.com>