backport: re PR fortran/46752 (OpenMP - Seg fault for unallocated allocatable array in firstprivate clause)

Merge from gomp-3_1-branch branch:

2011-08-02  Jakub Jelinek  <jakub@redhat.com>

gcc/
	* c-parser.c (enum c_parser_prec): New enum, moved from within
	c_parser_binary_expression.
	(c_parser_binary_expression): Add PREC argument.  Stop parsing
	if operator has lower or equal precedence than PREC.
	(c_parser_conditional_expression, c_parser_omp_for_loop): Adjust
	callers.
	(c_parser_omp_atomic): Handle parsing OpenMP 3.1 atomics.
	Adjust c_finish_omp_atomic caller.
	(c_parser_omp_taskyield): New function.
	(c_parser_pragma): Handle PRAGMA_OMP_TASKYIELD.
	(c_parser_omp_clause_name): Handle final and mergeable clauses.
	(c_parser_omp_clause_final, c_parser_omp_clause_mergeable): New
	functions.
	(c_parser_omp_all_clauses): Handle PRAGMA_OMP_CLAUSE_FINAL
	and PRAGMA_OMP_CLAUSE_MERGEABLE.
	(OMP_TASK_CLAUSE_MASK): Allow final and mergeable clauses.
	(c_parser_omp_clause_reduction): Handle min and max.
	*...