Fix for PR c++/PR39754

Fix for PR c++/PR39754

gcc/cp/ChangeLog:
    PR c++/39754
    * cp-tree.h (canonical_type_variant): Remove this function declaration.
    (strip_typedefs): New function declaration.
    * tree.c (strip_typedefs): New function definition.
    (canonical_type_variant): Remove function definition.
    * cvt.c (convert_from_reference): No need to use
    canonical_type_variant.
    * typeck.c (cp_build_indirect_ref): Likewise.
    * error.c (dump_template_bindings): Use strip_typedefs instead of
    canonical_type_variant.
    * pt.c (convert_template_argument, unify): Likewise.
    * mangle.c (canonicalize_for_substitution): Don't use
    canonical_type_variant.

gcc/testsuite/ChangeLog:
    PR c++/39754
    * g++.dg/template/canon-type-1.C: New test.
    * g++.dg/template/canon-type-2.C: Likewise.
    * g++.dg/template/canon-type-3.C: Likewise.
    * g++.dg/template/canon-type-4.C: Likewise.
    * g++.dg/template/canon-type-5.C: Likewise.
    * g++.dg/template/canon-type-6.C: Likewise.
    * g++.dg/template/canon-type-7.C: Likewise.

From-SVN: r147951