* include/stream_output.h: add a ip_version field to sap_address_t

* include/stream_output.h: add a ip_version field to sap_address_t
  This way we can later on set IP6 instead of IP4 in a SDP.
* modules/stream_out/rtp.c: accept sdp=sap as a valid option.
* src/stream_output/sap.c:
  - Set the SAP packet Hash headerfield to a unique value based on mtime
    Patch by Philippe van Hecke <philippe at belnet dot be>
  - Set SAP packet IPv6 field to 1 if we are a ipv6 session
  - Made some preperations for setting the origin ip address in the header as well,
    anyone any ideas on how to retrieve the current origin IP address???