MachineModuleInfo: Turn nested std::pairs into a proper struct.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@203414 91177308-0d34-0410-b5e6-96231b3b80d8
StackColoring: Use range-based for loops.

No functionality change.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@203415 91177308-0d34-0410-b5e6-96231b3b80d8