tabletserver: execution plan change

It appears that the MariaDB optimizer is not good at handling
tuple equalities for update statements. This cl changes the exection
plan of all tuple equalities from:
where (pk1, pk2) = (:v1, :v2) or (pk1, pk2) = (:v3, :v4) to
where (pk1 = :v1 and pk2 = :v2) or (pk1 = :v3 and pk2 = :v4), etc.
revert accidental Makefile change
Adding unit test for vtctl client-server protocols. Using it for gorpc.
Merge pull request #157 from youtube/suguwork

Suguwork
Merge pull request #160 from youtube/resharding

Making the test protocols easier to select with a command line parameter...
Merge pull request #159 from youtube/replication

Adding unit test for vtctl client-server protocols. Using it for gorpc.