This introduces {optimized_out} as another Oddball kind to be used by
optimizing compilers when values are being optimized away. The aim is
providing visibility when this value leaks into the application domain.
Currently this will lead to {undefined} values appearing which then
silently propagate through the application. The special oddball can be
identified easily as a bug and also the debugger can treat it specially
when needed.

R=jarin@chromium.org

Review URL: https://codereview.chromium.org/1810483002

Cr-Commit-Position: refs/heads/master@{#34817}