* Improved DiameterIdentity handling (esp. interationalization issues),
    and improve efficiency of some string operations in peers, sessions,
    and dictionary modules (closes #7)
  * Cleanup in the session module to free only unreferenced sessions (#16)
  * Removed fd_cpu_flush_cache(), replaced by more robust alternatives.
  * Improved peer state machine algorithm to counter SCTP multistream race
    condition.

Added Error-Cause attribute conversion in app_radgw.