First pass at primecache in go.

There is a feature test that allows us to run it and try it.
It doesn't work right now, mysqlbinlog doesn't return anything.
Merge branch 'master' into replication
Merge branch 'master' into replication
Working version of primecache.
More robust version, test is automated now.

(test uses sudo and takes a long time, so it's ot possible
to run all the time).
Removing a duplicate test.
Minor cosmetic changes, using a single channel.
Merge branch 'master' into replication