* Makefile.def: Remove libstdcxx_incdir, libsubdir, gxx_include_dir,
	gcc_version, and gcc_version_trigger from set of flags to pass.
	* Makefile.tpl: Remove definitions of above variables.
	(config.status): Remove dependency on $(gcc_version_trigger).
	* Makefile.in: Regenerate.
	* configure.in: Do not reference config/gcc-version.m4 nor
	config/gxx-include-dir.m4.  Do not invoke TL_AC_GCC_VERSION nor
	TL_AC_GXX_INCLUDE_DIR.  Do not set gcc_version_trigger.
	* configure: Regenerate.
config:
	* gxx-include-dir.m4: In all substitutions, leave $(gcc_version)
	to be expanded by the Makefile.