* version 0.9.6
  - added new option -j to add a header
  - added support for multiple variable replacement (option -g)
  - added support for SHA1 as digest algorithm for authentication
* version 0.9.5
  - renamed --invite-timeout to --timeout-factor
  - new option -E specifies the transport (UDP or TCP)
  - SRV lookup via c-ares is available
    (http://daniel.haxx.se/projects/c-ares/)
* version 0.9.2
  - prefers gnutls over openssl now
  - new option -D specifies the maximum INVITE timeout value
  - option -c specifies From header for MESSAGEs
* version 0.9.1
  - only fixes, no new options or features
* version 0.9.0
  - option -c in flood mode is replaced be -e
* version 0.8.13
  - SRV lookup is supported if libruli is available
    (http://www.nongnu.org/ruli/)
* version 0.8.12
  - numeric (-n) is now on by default
* version 0.8.11
  - try authentication with empty password instead of username if no
    password is given
  - support to read SIP message from standard input (-f -)
* version 0.8.10
  - send instant messages (just -M)
  - new argument -C to use any given contact value, even empty
  - support long options if available
  - support Nagios warn level with optional numbers of retransmissions
* version 0.8.6
  - important fixes
* version 0.8.5
  - ignores provisional responses in usrloc mode (-U)
  - added support for proxy authorization (407)
  - new argument -H overwrites automatic hostname detection
  - new argument -o introduces sleeping seconds before sending next request
  - number of retrys and maximum timeout values are configure options