to_string is not always available, so don't use it.

	libcody/
	* buffer.cc (MessageBuffer::AppendInteger): Workaround
	to_string's non-ubiquity.

libcody/ChangeLog:

	* buffer.cc (MessageBuffer::Lex): Remove unused variable.

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.