not finished, UE may not work, many things bad/to fix properly

[-1 29] was not very pleasant for MCS 28 or no DCI (value is -1 in this case).
[-2 30] looks better.

Helps visualize MCS usage over time.

When the user clicks on "next UE" or "prev UE" we change the
filters of loggers.

At the same time, the main thread of enb.c processes events
received from the soft-modem and uses the filters, some of them
maybe in the process of being changed.

Changing the filters is not atomic and has to be protected.

Just below the logo you see the current UE, eg. [UE 0],
and near that you have two "buttons" [prev UE] and [next UE].

You click with left button of mouse on those and the various
plots that depend on the UE are now done for the new UE (say UE 1
instead of UE 0 if you click on [next UE]).

The plots are not cleared when you switch.
Let's say it's a feature.

we have to free memory in any case...

XY_LOOP_MODE: replace old points with new ones, using the maximum size
              of the view
XY_FORCE_MODE: append_forced sets those and only those points
               and we crash if we pass too much points

very basic, to be refined, find a nice way to display (plot? text?)
protocol data movement

more readable, still not satisfying though

and also start to use the PHY textview

enb.c will then try to reconnect.

write() on a socket with the other end closed throws a SIGPIPE.
Let's ignore this signal. write() will return an error anyway...

fullread has been changed, so get_event too, and the callers also
for the moment the callers crash, enb.c will be a bit more clever,
the others to see...

The application (enb.c basically) will now monitor the socket
and reconnect if it dies. See following commits.

It was wrong.
Plus it is starting work so as to make enb.c not crashing if
the tracee goes away (maybe also textlog and vcd, but those are of
less importance).

The local tracer now waits for the remote tracer to connect,
that's no more the other way around.

All the remote tracers (textlog, enb, vcd) have also been converted.

can be deactivated on the command line or in the gui

- adding T macros here and there
- modify the T_messages.txt
- modify enb.c to trace them in the RRC view

plus add rrc connection setup complete tracing

as special events.

If we store all received events to a file, this dump is now
self-contained. Helps to analyze traces.

Some functions have also been factorized in the process, too much
duplication.

(Also tracer/Makefile was forgotten in previous commit, included
in this one...)