Fix PR 119928, formal arguments used to wrongly inferred for CLASS.

Fix PR 119928, formal arguments used to wrongly inferred for CLASS.

The problem was indeed that generating a formal from an actual
arglist is a bad idea when classes are involved.  Fixed in the
attached patch.  I think it still makes sense to remove the checks
when the other attributes are present (or PR96073 may come back
in different guise, even if I have to test case at present).
I have also converted the test to a run-time check.

gcc/fortran/ChangeLog:

	PR fortran/119928
	* interface.cc (gfc_check_dummy_characteristics): Do not issue
	error if one dummy symbol has been generated from an actual
	argument and the other one has OPTIONAL, INTENT, ALLOCATABLE,
	POINTER, TARGET, VALUE, ASYNCHRONOUS or CONTIGUOUS.
	(gfc_get_formal_from_actual_arglist): Do nothing if symbol
	is a class.

gcc/testsuite/ChangeLog:

	PR fortran/119928
	* gfortran.dg/interface_60.f90: New test.