Release candidate: 1.2.4-rc1

[dormando]

> I'll be sending a followup either later tonight or tomorrow with a merge
> of Dustin's external binary tree.

This obviously didn't happen; I did start reviewing the binary tree but 
some confusion with wbuf's, the holidays, and the broken mailing list 
set in some severe procrastinating.

Dustin's patches are at 
http://hg.west.spy.net/hg/hacks/memcached-binary/ if anyone else wants 
to jump in. They'll apply with a little wiggling, if not they're still 
good reading material.

But, please. Test 1.2.4-rc first, make sure it works! Clients are 
showing up with support for the new features, and we want to unleash the 
server part of that :)

-Dormando