Move isIdentifiedFunctionLocal from BasicAA to AA

The ability to identify function locals will exist outside of BasicAA (for
example, logic for inferring noalias function arguments will need this), so
make this concept generally accessible without code duplication.

No functionality change.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@213514 91177308-0d34-0410-b5e6-96231b3b80d8