Schedule discriminator pass.

This needs to modify a line table test to account for the new lexical
block created to hold the new discriminator value.

git-svn-id: http://llvm.org/svn/llvm-project/cfe/trunk@202754 91177308-0d34-0410-b5e6-96231b3b80d8
[C++11] Simplify compare operators with std::tie.

No functionality change.

git-svn-id: http://llvm.org/svn/llvm-project/cfe/trunk@202755 91177308-0d34-0410-b5e6-96231b3b80d8
[C++11] Add missing include.

git-svn-id: http://llvm.org/svn/llvm-project/cfe/trunk@202757 91177308-0d34-0410-b5e6-96231b3b80d8