Trying to dynamically track the DPI did not really work as we'd
start accumulating errors and eventually the DPI would start to
drift. Instead maintain a fixed, sensible DPI at all times.

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

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.

Mainly fixes for Japanese and Korean keyboard layouts.

This is needed by vncserver which doesn't know which parameters are
boolean, and it cannot use the -Param=Value form as that isn't tolerated
by the Xorg code.

It expects the callers to include this, so make sure we're consistently
providing one.

Major restructuring of how streams work. Neither input nor output
streams are now blocking. This avoids stalling the rest of the client or
server when a peer is slow or unresponsive.

Note that this puts an extra burden on users of streams to make sure
they are allowed to do their work once the underlying transports are
ready (e.g. monitoring fds).

External callers don't need to know the exact details, only if there is
data that needs to be flushed or not.

Might as well make these explicit so the cost is apparent.

This is the current upstream so let's make use of it to get the latest
in features and fixes.

It creates an invalid region if given an empty rect. Fortunately
RegionInitBoxes() handles that just fine, so use that instead.

We no longer support such old X servers so start using the current
functions.

It seems like many of the X11 operations can end up with no pixels
actually changing. So instead of discovering and adding workarounds for
each individually we'll just check very region added if it's empty.

We now require at least 1.16, so remove all code that handled older
versions than that.

We removed support in the code ages ago, but overlooked this part of the
documentation. Also remove some dead code in Xvnc on the same theme.

This sets up a more correct session as there are key tasks that
need to be performed by PAM. E.g. systemd will allocate cgroups
and start base services.

In order to easily handle this as a system service the mapping of
displays is now done via a configuration file.

This allows Xvnc to build with xorg-server 1.20.7, which requires OS
layers to implement a ddxInputThreadInit function when configured with
--enable-input-thread (the default).

relevant xorg-server commit: e3f26605d8

Don't allow subclasses to just override dimensions or buffer details
directly and instead force them to go via methods. This allows us
to do sanity checks on the new values and catch bugs and attacks.

In prepartion for better clipboard extensions that can send Unicode
data between the client and server.

Change the internal clipboard API to use a request based model in
order to be prepared for more advanced clipboard transfers.

We convert between UTF-8 and ISO 8859-1 (latin 1) in several places
so create some common routines for this.

We now filter incoming data, which means we can start assuming the
clipboard data is always null terminated. This allows us to clean
up a lot of the internal handling.

This is required by the protocol so we should make sure it is
enforced. We are tolerant of clients that violate this though and
convert incoming clipboard data.

There might be multiple clients using a single IP (e.g. NAT), which
can make the blacklist do more harm than good. So add a setting to
disable it if needed.

This is where to install headers to, not where to find headers to
build against. Toolchains should know where to locate their system
headers while non-system headers should be found using
pkg-config. Users with bizarre setups where the toolchain really
cannot find the system headers should set CPPFLAGS.

There is a range of key codes that are never sent by a real keyboard
and are therefore used by layouts to hide "fake" mappings. Make sure
to only use these as a fallback as some applications get confused
when they see these codes.

It doesn't belong on each socket server object as timers are global.
Force implementations to call the Timer system directly instead,
avoiding any middle men.

Do a proper cleanup when one of the termination timeouts trigger
rather than just exiting on the spot. This makes sure we don't leave
stray stuff around, e.g. unix socket files.

This makes VNCServer a sufficiently complete interface that callers
don't need to know about the specific implementation (VNCServerST
currently). And assuming that all servers will use sockets is not
that outrageous.

Our main web site now supports https, so update all references.

Make things simpler by making this a part of the SDesktop interface
that always needs to be implemented.

Force queryConnection() to always call back to approveConnection()
rather than return special values. This makes the flow easier to
follow as it will be the same in all cases.

Applets don't work anymore so remove everything that has to do
with serving them.

Most layouts on Unix generate Meta for Shift+Alt but non-Unix clients
will send XK_Alt_*. This results in us picking some other key which
can confuse some applications.

Try to detect this scenario and map XK_Alt_* to XK_Meta_*.

We get a whole bunch of very tiny areas, which is very inefficient to
deal with. Instead create a rectangle around every "list" of connected
glyphs (usually each line).

There are some cases where the server state will not automatically
be updated on a change. A prominent one is when only RFB attributes
were changes (e.g. the screen ID) but nothing else. In that case
there is no actual change in the X server, so it never sends any
notification about change back to us.

Function xorgGlxCreateVendor() is defined in glx_extinit.h, if this header is
not included, we might get either error or warning. This header also need to
be included after scrninststr.h header as it defines some structures used
in glx_extinit.h