[turbofan] Add support for Finish to the InstructionSelector.

Also fix an off-by-one bug in the handling of Parameter nodes, and
improve test coverage for pointer map computation.

TEST=compiler-unittest
R=titzer@chromium.org

Review URL: https://codereview.chromium.org/490673006

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@23219 ce2b1a6d-e550-0410-aec6-3dcde31c8c00