Baby steps towards migrating the InitListChecker over to the new...

Baby steps towards migrating the InitListChecker over to the new initialization code. Pass an InitializedEntity pointer through to most init checker functions. Right now, it's ignored everywhere except when initializing vectors in C++.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@94325 91177308-0d34-0410-b5e6-96231b3b80d8