socket_pcap: Fixes pcap filter creation
socket_pcap: Fixes pcap filter creation

* Previously, you had to set a capture_filter param in order to have
  reassembly enabled
* Now you need a filter set for reassembly to work
* Restructured the code and removed code duplication (pcap_compile)
* Still probably buggy: when using capture_filter in addition to
  normal filters, the normal filters should be enclosed in brackets
  or the "and" of the filter will break the rest

sipcapture/captagent,sipcapture/captagent,sipcapture/captagent