Use the correct frame when evaluating a dynamic property

The test case in this patch shows an unusual situation: an Ada array
has a dynamic bound, but the bound comes from a frame that's referred
to by the static link.  This frame is correctly found when evaluating
the array variable itself, but is lost when evaluating the array's
bounds.

This patch fixes the problem by passing this frame through to
value_at_lazy in the DWARF expression evaluator.