Rework C/C++ OpenACC routine parsing

Rework C/C++ OpenACC routine parsing

	gcc/c/
	* c-parser.c (struct oacc_routine_data): Add error_seen and
	fndecl_seen members.
	(c_finish_oacc_routine): Use these.
	(c_parser_declaration_or_fndef): Adjust.
	(c_parser_oacc_routine): Likewise.  Support more C language
	constructs, and improve diagnostics.  Move pragma context
	checking...
	(c_parser_pragma): ... here.
	gcc/cp/
	* parser.c (cp_ensure_no_oacc_routine): Improve diagnostics.
	(cp_parser_late_parsing_cilk_simd_fn_info): Fix diagnostics.
	(cp_parser_late_parsing_oacc_routine, cp_finalize_oacc_routine):
	Simplify code, and improve diagnostics.
	(cp_parser_oacc_routine): Likewise.  Move pragma context
	checking...
	(cp_parser_pragma): ... here.
	gcc/testsuite/
	* c-c++-common/goacc/routine-5.c: Update.

From-SVN: r239128