pjsip: Update bundled PJSIP to revision 4578

Ignore-this: ea4018bdf1f63e531bfd41de3d64f97b

darcs-hash:20130806103243-56b4d-f7538e8746e5d193515595d5416e7018eae9bfab
Adapted re-INVITE handling after API changes in PJSIP

Ignore-this: 9100acd7532aa7bc5401bd82db22d2b9

darcs-hash:20130806103329-56b4d-bba83dcc8b443d5e8e69510acab8ca29cfef1a8f