This is a followup to my recent coarray/scalarizer changes, especially that one
cleaning-up gfc_walk_variable_expr/gfc_walk_array_ref:
http://gcc.gnu.org/ml/fortran/2011-09/msg00072.html
Scalar coarrays are not handled as AR_ELEMENT in the scalarizer.
Thus, no need to handle coarrays here.
OK?