re PR c++/13140 (declaration in global namespace, definition inside named or anon namespace)
PR c++/13140
* decl.c (check_class_member_definition_namespace): New function.
(grokfndecl): Use it.
(grokvardecl): Likewise.
(grokdecl): Improve documentation.
* pt.c (check_explicit_instantiation_namespace): New function.
(register_specialization): Call check_specialization_namespace
when replacing an implicitly instantiated function.
(check_explicit_specialization): Ensure that DECL_CONTEXT is set
correctly for namespace-scope specializations.
(do_decl_instantiation): Use
check_explicit_instantiation_namespace.
(do_type_instantiation): Likewise.