The following builds with -std=c++11 and c++14 and c++17 and c++20 and c++23
and c++26.

I see the u8 string literals are mixed e.g. with strerror, so in
-fexec-charset=IBM1047 there will still be garbage, so am not 100% sure if
the u8 literals everywhere are worth it either.

2025-11-21  Jakub Jelinek  <jakub@redhat.com>

	* cody.hh (S2C): For __cpp_char8_t >= 201811 use char8_t instead of
	char in argument type.
	(MessageBuffer::Space): Revert 2025-11-15 change.
	(MessageBuffer::Append): For __cpp_char8_t >= 201811 add overload
	with char8_t const * type of first argument.
	(Packet::Packet): Similarly for first argument.
	* client.cc (CommunicationError, Client::ProcessResponse,
	Client::Connect, ConnectResponse, PathnameResponse, OKResponse,
	IncludeTranslateResponse): Cast u8 string literals to (const char *)
	where needed.
	* server.cc (Server::ProcessRequests, ConnectRequest): Likewise.

Fix some more system-specific issues.  Not everyone's C++11 is the same :(

	PR bootstrap/98412
	libcody/
	* client.cc: Include cstdlib.
	* server.cc: Include cstdlib.
	gcc/cp/
	* mapper-client.cc: INCLUDE_STRING, INCLUDE_VECTOR.
	(module_client::open_module_client): Avoid std::stoul.
	* mapper-resolver.cc: INCLUDE_STRING, INCLUDE_VECTOR.

In order to separate compiler from build system, C++ Modules, as
implemented in GCC introduces a communication channel between those
two entities.  This is implemented by libcody.  It is anticipated that
other implementations will also implement this protocol, or use
libcody to provide it.

	* Makefile.def: Add libcody.
	* configure.ac: Add libcody.
	* Makefile.in: Regenerated.
	* configure: Regenerated.
	gcc/
	* Makefile.in (CODYINC, CODYLIB, CODYLIB_H): New. Use them.
	libcody/
	* configure.ac: New.
	* CMakeLists.txt: New.
	* CODING.md: New.
	* CONTRIB.md: New.
	* LICENSE: New.
	* LICENSE.gcc: New.
	* Makefile.in: New.
	* Makesub.in: New.
	* README.md: New.
	* buffer.cc: New.
	* build-aux/config.guess: New.
	* build-aux/config.sub: New.
	* build-aux/install-sh: New.
	* client.cc: New.
	* cmake/libcody-config-ix.cmake
	* cody.hh: New.
	* config.h.in: New.
	* config.m4: New.
	* configure: New.
	* configure.ac: New.
	* dox.cfg.in: New.
	* fatal.cc: New.
	* gdbinit.in: New.
	* internal.hh: New.
	* netclient.cc: New.
	* netserver.cc: New.
	* packet.cc: New.
	* resolver.cc: New.
	* server.cc: New.
	* tests/01-serialize/connect.cc: New.
	* tests/01-serialize/decoder.cc: New.
	* tests/01-serialize/encoder.cc: New.
	* tests/02-comms/client-1.cc: New.
	* tests/02-comms/pivot-1.cc: New.
	* tests/02-comms/server-1.cc: New.
	* tests/Makesub.in: New.
	* tests/jouster: New.