rtl-ais/tcp_listener

Use tcp listener service insted of udp.
These files are compiles into a library and a tcp server has the advantage that more clients can access AIS data from the same server.
The tcp_listener is tested under raspbian jessie on a raspberry pi with 5 concurrent connections.
Tested on OpenCPN.
Rtl-ais runs excactly as before using udp if the -T option is not supplyed. 

New options:
Use: rtl_ais [options] [outputfile]
...
      [-T use TCP communication ( -h is ignored)
      [-t time to keep ais messages in sec, using tcp listener (default: 15)
...


TODO: Fix to run under OSX and Windows. (I'll do the windows part if others find it usefull) 
      Makefile must be included in rtl-ais Makefile
      Merge of rtl-ais.c, aisdecoder.c and aisdecoder.h if it is found usefull.
      Daemonize rtl-ais. (I'll do it if others find it usefull)