3 available mechanisms: by public key, by host name, and by certificate subject name.
In the former method, chain of trust verification is not performed.
The CA certificate files are looked for under <spice-config-dir>/spice_truststore.pem
windows <spice-config-dir>=%APPDATA%\spicec\
linux <spice-config-dir>=$HOME/.spicec/
The process loop is responsible for: 1) waiting for events 2) timers 3) events queue for
actions that should be performed in the context of the thread and are pushed from other threads.
The benefits:
1) remove duplicity: till now, there was one implementaion of events loop for the channels and
another one for the main thread.
2) timers can be executed on each thread and not only on the main thread.
3) events can be pushed to each thread and not only to the main thread.
In this commit, only the main thread was modified to use the new process loop.
