[Serdev] [Patch] Ability to check negative reply code in the failure_route

[Maxim Sobolev]

Folks,

I've found it quite limiting that there is no way to check SIP response 
code that has lead to execution of failure_route routine. For example 
when implementing VM one certainly would want to filter out 487 and 
probably all 3xx class replies.

I've put together small patch which adds new keyword - failure_status 
that can be checked just like status, but in the failure_route. Please 
review. Any comments or suggestions are appreciated. Patch can be found 
here:

http://www.portaone.com/~sobomax/ser_failure_code.diff

-Maxim