[reSIProcate] directory reorg

[david Butcher <davidlbutcher@xxxxxxxxx>]

Hi all,

We haven't picked at this scab for a while. I would like to propose a
directory structure for resiprocate.

resip/dns
resip/dns/test
resip/dum
resip/dum/test
resip/os
resip/os/test
resip/repro
resip/repro/test
resip/sip
resip/sip/test
resip/util
resip/util/test

My understanding is that msrp is off in its own repository. 

Things to notice:
 - the stack proper is in repro/sip
 - os and util are separated
 -- Mutex, Condition, etc. will be in resip/os
 -- Data, DataStream, ParseBuffer, etc. are in resip/util
 - tests are separated

david