[analyzer] Dynamic type info - propagate through implicit casts.

I currently have a bit of redundancy with the cast kind switch statement
inside the ImplicitCast callback, but I might be adding more casts going
forward.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@161358 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed