[turbofan] Add support for change/truncate to MachineOperatorReducer.

TEST=compiler-unittests
R=jarin@chromium.org

Review URL: https://codereview.chromium.org/470633006

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@23293 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Add missing test directories to presubmit.py.

R=machenbach@chromium.org
BUG=v8:3489
LOG=n

Review URL: https://codereview.chromium.org/479503004

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@23294 ce2b1a6d-e550-0410-aec6-3dcde31c8c00