When a message has been read from the network we now pass it into
the generated demarshaller for the channel. The demarshaller converts
the network data to in-memory structures that is passed on to the
spice internals.
Additionally it also:
* Converts endianness
* Validates sizes of message and any pointers in it
* Localizes offsets (converts them to pointers)
* Checks for zero offsets in messages where they are not supported
Some of this was previously done using custom code in the client, this
is now removed.
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.
