CoqIDE: show error message for parsing errors
STM: restart slave after every proof

The code now passes a cleanup function that, if slave is not
killed, could be used to do some cleanup between two jobs.

ATM I don't know how to reuse the worker without having it
grow in space indefinitely.  Running Gc.compact is too expensive.
Reduction: every n iterations a slaves process checks for interruption

I chose n to be 10000 iterations.  It might be big, but a slave, to check
for a termination request, has to pass the ball to the thread that
sends "regularly" Ticks to the master process.  Thread.yield is a
system call, so we have to do it very rarely.
Use my real email address in .mailmap
First stab at retrocompatible INTERP message
New option --help-XML-protocol to document the XML procol used by -ideslave

Serialize.ml spits out its own documentation.  Not everything is
statically checked, so it risks to get outdated.  Ideas on how
to statically/dynamically check that the doc is in sync are welcome.