<rdar://problem/13621080>

This commit changes the ${function.name-with-args} prompt keyword to also tackle structs
Previously, since aggregates have no values, this would show up as foo=(null)
This checkin changes that to instead print foo=(Foo at 0x123) (i.e. typename at address)
There are other potential choices here (summary, one-liner printout of all members, ...) and I would love to hear feedback about better options, if any