c-parser.c (c_parser_translation_unit): Diagnose declare target without corresponding end declare target.

	* c-parser.c (c_parser_translation_unit): Diagnose declare target
	without corresponding end declare target.

	* semantics.c (finish_translation_unit): Diagnose declare target
	without corresponding end declare target.

	* c-c++-common/gomp/declare-target-5.c: New test.

From-SVN: r278065