hast vs ggate+gmirror sychrnoisation speed

[Pete French]

Just to report back on this - I just tried the patches from last week,
which fixed the sending of the keepalives in the different
thread, but my original issue (the sychronisation speed) remains
I'm afraid - so much for the theory that the corruption was causing
the speed decrease. It's obviously good to have the threading issue
fixed though.

-pete.