re PR preprocessor/27746 (ICE on openmp code when using _Pragma from macro)

	PR preprocessor/27746
	* directives.c (do_pragma): Handle pragma with valid namespace
	and invalid name coming from macro expansion.
	* directives.c (destringize_and_run): Initialize next field in
	context.

	PR c/27747
	PR c++/27748
	* directives.c (destringize_and_run): Set NO_EXPAND on the
	tokens.

	* macro.c (_cpp_backup_tokens): Fix comment typo.
testsuite/
	PR c/27747
	* gcc.dg/cpp/_Pragma6.c: New test.

	PR c++/27748
	* g++.dg/cpp/_Pragma1.C: New test.

	PR preprocessor/27746
	* gcc.dg/gomp/macro-3.c: New test.
	* gcc.dg/gomp/macro-4.c: New test.
	* g++.dg/gomp/macro-3.C: New test.
	* g++.dg/gomp/macro-4.C: New test.

From-SVN: r114519