Added building instructions for MacOSX 10.8 Mountain Lion

Ignore-this: c8f7e24980ac963aedb15b21499864c2

darcs-hash:20130417081857-58252-fa844d7de91cb12a0efbe5d25a75eafe645a3858
Remove references to OSX 10.8 from 10.7 build instructions

Ignore-this: 7cfb2dc701aef74164375d7759e82466

darcs-hash:20130417082015-58252-6286caeb25d5aecd898df4f8ccd2e6642d4c1d51
Fixed parsing sip.instance from a REGISTER reply

Ignore-this: 1a4ccdce25c194f992f7f02d83461894

darcs-hash:20130429091220-56b4d-aab1937d7396b195c933f312fc35e603dc812a08