Added feature to suspend pcapdj via SIGUSR1

If the signal SIGUSR1 is sent to PCAPDJ, it stops feeding the named
pipe with pcap packets
SIGUSR2 shows processing statistics and internal states

When SIGUSR2 is sent to pcapdj the following information is displayed

Example:

[STATS] Start time:2013-06-09 09:17:50
[STATS] Uptime:423 (seconds)
[STATS] Internal state:Waiting for authorization
[STATS] Number of suspensions:0
[STATS] Number of files:2
[STATS] Number of packets:6346
[STATS] Number of cap_lengths:706730
[STATS] Number of lengths:706730
Took over old README.md
Merge branch 'master' into experimental
Experimental features are merged in the master version