These are not allowed in C++, and have been made optional in C11.
So let's just get rid of them and any issues they may cause.

Avoid using the callbacks used for runtime changes for the initial
setup. They weren't really useful anyway as you could not allocate
a framebuffer without also knowing the pixel format. So make things
more clear by letting serverInit() get the initial settings.

Now that we've split out server state to ServerParams, ConnParams
only contains state for a client. Rename the class and variables
to reflect this.

We need to track different things in the server and client, so
separate things to two independent structures to keep things more
clear.

Avoid direct access to the screen dimensions and layout so that we
can make sure it stays sane. This also makes sure the layout is
properly updated when we only get the screen dimensions from the
server.

We use polymorphic exception objects, so catching by value invokes
the copy constructor and stuff that we don't really want.

This will allow us to use better formats that preserve the entire
alpha channel.

This is based on comparing CPU time with elapsed time, which means
that the tests can be heavily influenced by other load on the test
machine.

We need more callbacks for correct operation of multi-threaded
rect decoding.

Done in preparation for multi-core decoding. Keeps the complexity
out of the other classes. This also moves ownership of the
framebuffer in to CConnection. It's the CConnection object that is
aware of the threads and how to synchronise with them. Therefore
the ownership of the framebuffer must also be there to make sure
it isn't deleted whilst threads are working.

It doesn't really make sense anymore given that settings might come
from the GUI or configuration and not only the command line.

This prevents unhandled exceptions if the file isn't found.

For 16-bit and 8-bit datasets, you can now run encperf with an argument of
-translate=0 to benchmark just the encoder without converting the datasets to
24-bit.  This allows the output of encperf to be directly compared with that
of the TurboVNC Benchmark Tools.

GCC lets this slide, but other compilers (clang) complain about using % rather
than %% to print a literal % character.

Explicitly add the compression level to the list of encodings so it's obvious
how to override it.

Report encoded and raw-equivalent bytes as well as compression ratio (I like
to have these statistics so I can compute overall compression ratios for
groups of datasets in a spreadsheet.)

Code formatting tweaks to improve readability & make the code consistent with
the rest of TigerVNC