This ensures the class in question specifies the correct equality and
hashing function when instantiated. Note that this introduces two new
structs (i.e. OpEqualTo and OpHash) which can be used for defaults
within OpParameter as well.

R=titzer@chromium.org,bmeurer@chromium.org
TEST=cctest/test-operator

Review URL: https://codereview.chromium.org/1455913003

Cr-Commit-Position: refs/heads/master@{#32080}