Add iterator_range for MachineInstr defs.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@206238 91177308-0d34-0410-b5e6-96231b3b80d8
[ARM64,C++11]: Range'ify the dead-register-definition pass.

Range-based for loops. No functional change intended.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@206239 91177308-0d34-0410-b5e6-96231b3b80d8