Make state enum private
New torcontrol relay ping module

This module extends a new circuit to the relay specified in the XML
program args, and measure the time until the circuit has been extended.
The circuit is then torn down. This can be used to measure the
approximate RTT through the relay.

NOTE: the torcontrol application must be started with enough delay after
the Tor client is started to give the client enough time to download the
relay descriptors.
Track ping circuits directly by circ id

This fixes our ping tracking code so we are matching ping start and end
times according to the actual circuit id of the circuit that we created.
dont remove ping on events we dont care about, like LAUNCHED
ask to proceed after download / sig check
Add stop application functionality

Applications that nodes run can now be stopped at a time specified
in the XML hosts file. The new application attribute looks like
stoptime="1234". The plugin_free function will be called at that
time to "shutdown" the application. It has been written such that
the application COULD be later restarted, though there is currently
no way to specify this in the XML file.

Also, application start times were previously specified with time="123".
Although still currently accepted, the 'time' attribute for applications
are now deprecated. Use the 'starttime' attribute instead.
change log levels

tcp_autotune to info level from debug
node_new to message level from info
Check glibc header version for getnameinfo

fixes #109