This fixes regression introduced by the extended clipboard extension.
Previously it was possible for the server to hold on to the CLIPBOARD
selection even if another application took ownership of PRIMARY. This is
important to handle the common use case of selecting something in order
to paste over it.

The new request based model doesn't readily support this as we assume
the client has lost its data once we push the new PRIMARY selection to
it. So to handle this we have the maintain a cache of the client's data,
and make sure to fill that cache before we do anything that might cause
the client to lose the data.

I am cross-compiling from macOS for a FreeBSD-derived system so my host
file system is case insensitive but the target isn't. Without this change
I get the following warnings which show that the vnc "Input.h" is being
included from mi/mi.h instead of the xserver "input.h":
```
In file included from /Users/alex/cheri/xvnc-server/hw/vnc/Input.c:33:
/Users/alex/cheri/xvnc-server/mi/mi.h:55:10: warning: non-portable path to file '"Input.h"'; specified path differs in case from file name on disk [-Wnonportable-include-path]
#include "input.h"
         ^~~~~~~~~
         "Input.h"
```

Some operating systems such as FreeBSD don't define a HOST_NAME_MAX
macro. The portable approach to determine the real host name limit is
calling sysconf(_SC_HOST_NAME_MAX) so do that instead.

Xvnc was originally based on Xvfb, but it's just confusing to keep the
names. So change all prefix to "vnc" instead to clearly mark things as
part of TigerVNC.

It isn't really useful as it behaves just like starting multiple
servers, so remove it in favour of keeping things simple.

This is a development flag with no real use, so remove it to clean up
the code.

Remove stuff we don't use, and get it more in sync with Xvfb for easier
comparison.

This was removed years ago.

The memory leak this worked around was fixed in X.org 1.16.

Keep everything in one place to make it easier to read.

This also removes the call to RRInit() as that is done implicitly
anyway.

There's been a common one since X.org 1.11, so use that instead of our
own copy.

We don't build for that platform anyway, so this is just a remnant from
Xvfb.

With the 1.20.x releases there has been features and API changes even on
patch level versions, so we need to update our macros to handle these as
well.

This is a pointless remnant of Xvfb. We never print the id of the shared
memory, so no other application can access this memory anyway.

This hasn't been supported or used in many years, so clean out the final
remnants.

This hasn't been used since xorg-server 1.1 so get rid of it.

This is consistent with other ddx behaviour.

This is what all the other ddx variants use, so do the same in Xvnc to
be consistent.

Makes it easier to compare with upstream files as the formatting will be
the same.

RENDER has been mandatory since xorg-server 1.9, so remove these
checks.

This should only be in the ddx parts of an X server, and Input.c is used
by libvnc.so as well and can cause conflicts there.

We miscalculated the screen layout if the geometry had an offset as we
adjusted the real screen layout to account for the offset, but compared
it to the unadjusted geometry.

Is a lot more useful default than the previous "x11", or "x0vncserver".
At the same time give x0vncserver a parameter to change the name.

Better to just hide these parameters rather than stating that they are
unused in the man page.

Give people a chance to know about the documentation.

It's almost mandatory to specify "session", but fairly rare to need to
set "desktop", so let's tweak the examples to avoid confusion and
mistakes.

The new vnc_home_t type for HOME/.vnc directory was added to the policy,
backed by a name transition. The vnc_session_t domain can manage files
and directories of this type.

The permissions set to manage directories and files with the nfs_t type
is allowed when the use_nfs_home_dirs boolean is turned on.

Resolves: https://github.com/TigerVNC/tigervnc/issues/1189

Sections and rules blocks reordered according to the Style guide.

https://github.com/TresysTechnology/refpolicy/wiki/StyleGuide

Style guide [1] issues only. No impact on policy functionality.

[1] - https://github.com/TresysTechnology/refpolicy/wiki/StyleGuide

Build flags control where this file ends up, so avoid assuming a
specific path in the HOWTO.

The line width was very inconsitent in this file, so standardise on the
common 72 characters.

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.

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

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.

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.