Fix fortran scalar elemental dependency mishandling

Fix fortran scalar elemental dependency mishandling

	PR fortran/66089
gcc/fortran/
	* trans-expr.c (expr_is_variable, gfc_expr_is_variable): Rename
	the former to the latter and make it non-static.  Update callers.
	* gfortran.h (gfc_expr_is_variable): New declaration.
	(struct gfc_ss_info): Add field needs_temporary.
	* trans-array.c (gfc_scalar_elemental_arg_saved_as_argument):
	Tighten the condition on aggregate expressions with a check
	that the expression is a variable and doesn't need a temporary.
	(gfc_conv_resolve_dependency): Add intermediary reference variable.
	Set the needs_temporary field.
gcc/testsuite/
	* gfortran.dg/elemental_dependency_6.f90: New.

From-SVN: r233188