* EXOSIP_OPT_SET_MAX_MESSAGE_TO_READ: set the number of message to read at once for each network processing.
* EXOSIP_OPT_SET_MAX_READ_TIMEOUT: set the period in nano seconds during we read for sip message.
* EXOSIP_OPT_GET_STATISTICS: retreive numerous statistics.
* optimize all loops by using osip iterator to improve performance.
Improve autotools, ./configure, Makefile.am
* modify --enable-pthread options (sync with osip)
* modify --enable-semaphore options (sync with osip)
* better order of link/flags, avoid duplicate at compile/link time
* rename -DHAVE_CARES_H to -DHAVE_ARES_H (real name of head)
