Templatify DominanceFrontier.

Theoretically this should now work for MachineBasicBlocks.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@212885 91177308-0d34-0410-b5e6-96231b3b80d8
Try to fix MSVC build

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@212886 91177308-0d34-0410-b5e6-96231b3b80d8