Allow the pjsip build directory to be specified from environment

darcs-hash:20090413153348-b22ec-21d39a69151b3ec1130f8ebadc9efd75980c66d0
Renamed Testing.txt to Clients.txt

darcs-hash:20090413171335-b22ec-2d7b8b27fd424dd09b4eae3edaec9f4222b9b10e