The following patch attempts to implement what apparently clang++
implemented for explicit object member function mangling, but nobody
actually proposed in patch form in
https://github.com/itanium-cxx-abi/cxx-abi/issues/148

2024-01-13  Jakub Jelinek  <jakub@redhat.com>

gcc/cp/
	* mangle.cc (write_nested_name): Mangle explicit object
	member functions with H as per
	https://github.com/itanium-cxx-abi/cxx-abi/issues/148 non-proposal.
gcc/testsuite/
	* g++.dg/abi/mangle79.C: New test.
include/
	* demangle.h (enum demangle_component_type): Add
	DEMANGLE_COMPONENT_XOBJ_MEMBER_FUNCTION.
libiberty/
	* cp-demangle.c (FNQUAL_COMPONENT_CASE): Add case for
	DEMANGLE_COMPONENT_XOBJ_MEMBER_FUNCTION.
	(d_dump): Handle DEMANGLE_COMPONENT_XOBJ_MEMBER_FUNCTION.
	(d_nested_name): Parse H after N in nested name.
	(d_count_templates_scopes): Handle
	DEMANGLE_COMPONENT_XOBJ_MEMBER_FUNCTION.
	(d_print_mod): Likewise.
	(d_print_function_type): Likewise.
	* testsuite/demangle-expected: Add tests for explicit object
	member functions.