Convert the PBX core to use read/write locks. This yields a nifty performance...

Convert the PBX core to use read/write locks. This yields a nifty performance improvement when it comes to simultaneous calls going through the dialplan. Using murf's test the old mutex based core took an average of 57.3 seconds while the rwlock based core took 31.1 seconds. That's a nifty 26.2 seconds performance improvement. The other good part is that if we do need to switch back then we just have to change the lock/unlock API calls. I converted everywhere that used to touch the mutex locks directly to use them.


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@57184 65c4cc65-6c06-0410-ace0-fbb531ad65f3