Initial import of libtrace 3.0.0

Initial import of libtrace 3.0.0

libtrace is a library for trace processing. It supports multiple input methods,
including device capture, raw and gz-compressed trace, and sockets; and
multiple input formats, including pcap and DAG.

Features
* Understands PCAP, ERF, DAG, legacy POS, ATM and Ethernet and preliminary
  WAG formats
* Read from tracefile, gz-compressed tracefile
* Native DAG read support
* BPF filter support on all input formats
* Format conversion into ERF and PCAP formats
* Write to tracefile for all formats
* Write to interface via PCAP or Natively under Linux
* libpacketdump, a packet dumping library useful for diagnosis
* Various tools for trace manipulation