* gdbtypes.c (make_qualified_type): Doc fix. Add assertion to

* gdbtypes.c (make_qualified_type): Doc fix.  Add assertion to
prevent cross-objfile references.
(make_cv_type): Doc fix.  Don't create cross-objfile references,
even for stub types.
(replace_type): Add assertion to prevent cross-objfile references.
(check_typedef): Never resolve a stub type by copying over a type
from another file.