* pt.c (resolve_overloaded_unification): New fn.
(try_one_overload): Likewise.
(unify): Don't fail on unknown type.
(type_unification_real): Likewise. Use resolve_overloaded_unification
to handle an overloaded argument.
(template_args_equal): Split out...
(comp_template_args): From here.
(determine_specialization): Also allow a template with more
parms than were explicitly specified.
* cp-tree.h: Add template_args_equal.
* call.c (resolve_args): Remove TEMPLATE_ID_EXPR code.