Add SystemZ feats to CodeGenerator.rst


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@181431 91177308-0d34-0410-b5e6-96231b3b80d8
Add myself as SystemZ code owner


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@181434 91177308-0d34-0410-b5e6-96231b3b80d8
For r181148: fixed warning 'enumeral and non-enumeral type in conditional expression'.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@181437 91177308-0d34-0410-b5e6-96231b3b80d8