Add pass-manager flags to use CFL AA

Add -use-cfl-aa (and -use-cfl-aa-in-codegen) to add CFL AA in the default pass
managers (for easy testing).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@216978 91177308-0d34-0410-b5e6-96231b3b80d8
[CFLAA] constexpr -> LLVM_CONSTEXPR

Attempt to fix the MSVC build by not using constexpr.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@216979 91177308-0d34-0410-b5e6-96231b3b80d8