pjsip: Use sizeof instead of hardcoded value for memory computations

Ignore-this: 997a99ed7c2a3c0ac78712846d3d0628

darcs-hash:20130723073204-b22ec-ca79d14438e01bc333728c7ecb3d638792b67585
pjsip: Removed unnecessary reset of the echo canceller temporary frame

Ignore-this: 236522f38447c0e30e303c75002ad4ab

darcs-hash:20130723074803-b22ec-221146704734e0730357c44c0ce7a07764b49ab2
pjsip: Fixed code indentation

Ignore-this: 2ff50e28405085df833c1720e8cf69d1

darcs-hash:20130723095559-b22ec-1f495583242798092887e2bfa09b39982fbdf2fa