Clean up r156925, so that we only mark the capturing DeclRefExpr of a

lambda as referring to a local in an enclosing scope if we're in the
enclosing scope of the lambda (not it's function call operator). Also,
turn the test into an IR generation test, since that's where the
crashes occurred. Really fixes PR12746 / <rdar://problem/11465120>.

llvm-svn: 156926