Temporary fix for PR18473: Don't try to evaluate the initializer for a
type-dependent variable, even if the initializer isn't value-dependent. This
happens for ParenListExprs composed of non-value-dependent subexpressions, for
instance.

We should really give ParenListExprs (and InitListExprs) the type of the
initialized entity if they're used to represent a dependent initialization (and
if so, set them to be type-, value- and instantiation-dependent).
Convert test to FileCheck.