The main.c code is responsible for initialization and shutdown;
the mainloop.c code is responsible for running the main loop of Tor.
Splitting the "generic event loop" part of mainloop.c from the
event-loop-specific part is not done as part of this patch.
There are now separate modules for:
* the list of router descriptors
* the list of authorities and fallbacks
* managing authority certificates
* selecting random nodes
