Fortran: Fix checking for IMPURE in DO CONCURRENT.

Fortran: Fix checking for IMPURE in DO CONCURRENT.

	PR fortran/119836

gcc/fortran/ChangeLog:

	* resolve.cc (check_pure_function): Fix checking for
	an impure subprogram within a DO CONCURRENT construct.
	(pure_subroutine): Ditto.

gcc/testsuite/ChangeLog:

	* gfortran.dg/do_concurrent_all_clauses.f90: Remove invalid
	dg-error test.
	* gfortran.dg/pr119836_1.f90: New test.
	* gfortran.dg/pr119836_2.f90: New test.
	* gfortran.dg/pr119836_3.f90: New test.
	* gfortran.dg/pr119836_4.f90: New test.

(cherry picked from commit f9ea46d946887a05d7ecbca5aeeb99fd868f6e70)