Thanks @Raulkumar for finding this in #1118

This change makes it possible for re-synchronizing the remote cursor on
the vncviewer when in fullscreen mode. This is done by locally moving
the cursor position to what the server thinks it should be.

Now SDL games should work!

stderr has been redirected to /dev/null so all logging needs to go to
syslog.

This change adds support for the VMware Mouse Position
pseudo-encoding[1], which is used to notify VNC clients when X11 clients
call `XWarpPointer()`[2]. This function is called by SDL (and other
similar libraries)  when they detect that the server does not support
native relative motion, like some RFB clients.

With this, RFB clients can choose to adjust the local cursor position
under certain circumstances to match what the server has set. For
instance, if pointer lock has been enabled on the client's machine and
the cursor is not being drawn locally, the local position of the cursor
is irrelevant, so the RFB client can use what the server sends as the
canonical absolute position of the cursor. This ultimately enables the
possibility of games (especially FPS games) to behave how users expect
(if the clients implement the corresponding change).

Part of: #619

1: https://github.com/rfbproto/rfbproto/blob/master/rfbproto.rst#vmware-cursor-position-pseudo-encoding
2: https://tronche.com/gui/x/xlib/input/XWarpPointer.html
3: https://hg.libsdl.org/SDL/file/28e3b60e2131/src/events/SDL_mouse.c#l804

Or rpmbuild gets grumpy.

This reverts commit d6e39658ae. Apparently
this is broken on macOS so it's not something we can make use of.

Some of these were incorrectly calculated so the server or client would
wait too long before proceeding with decoding.

Change all of these to be a more explicit calculation to avoid such
issues in the future.

TCP_CORK is a Linux thing and BSD has TCP_NOPUSH instead.

We didn't include the proper headers to get the correct define, so
corking was never enabled.

Otherwise we might end up owners of something we cannot deliver data on,
which can hang applications.

Setting `rfbport` to `-1` disables TCP port listening.

It took way too long to converge on a sane value, so reduce the window
by a factor of ten. This seems to work smoothly.

So that people can easily find them and not file bug reports for
things that are just questions.

We want users to use the templates so we don't miss any relevant
information.

We computed a safe area if a client gave us a bogus one, but we didn't
actually use it. Fix this properly and make sure we don't pass on bad
coordinates further.

So the current clipboard state is properly reflected in the desktop
session.

This was out of sync with the client handling for no good reason.

The peer expects a response, so we should also be able to respond that
there is no clipboard data currently available.

The extended clipboard protocol has the ability for the peer to request
things to be sent automatically, without a request message. Make sure we
honor such settings.

It's a better match for what the key symbolises, even though it is not
as common on Unix systems. But we want to avoid getting in to tailoring
things for any one specific input method implementation.

We don't know the size of the output buffer here and giving the input
string size is just confusing and upsets the compiler in some cases.

This is what display managers do, so it is expected by many
environments.

We terminated the child instead of the parent after fork().

Reported by Jan Grulich from Red Hat.

Windows either completely omits WM_KEYUP for these, or only sends it
just before the next WM_KEYDOWN for the key.