cpphash.h (struct spec_nodes): Add n_true and n_false.

cpphash.h (struct spec_nodes): Add n_true and n_false.

	* cpphash.h (struct spec_nodes): Add n_true and n_false.
	* cppinit.c (cpp_create_reader): Initialize them.
	(append_include_chain): cxx_aware arg might be unused.
	* cppexp.c (lex): In C++ mode, recognize 'true' and 'false'
	keywords and give them their phase 7 meaning.  Pedwarn about
	this unless '__bool_true_false_are_defined' is defined.

	* g++.dg/stdbool-if.C: New test.

From-SVN: r39530