Change Xserver screen through libXrandr. For complex configurations,
all outputs must have corresponding size modes. As a special case, if
the client requests a single screen with an odd size (for example when
adjusting the size of a non-fullscreen vncviewer), find a smaller
suitable mode, and reduce the framebuffer size as well.

This can be used to test if a layout if possible.

Better to avoid making unnecessary calls, but mainly we want to avoid
logging false errors.

For example, if we have earlier disabled an output because it was too
large for the framebuffer, we should prefer this output when
allocating new outputs.

Move the code that turn off unused outputs to the end.

Also, add support for checking the output connection state.

Apparently this is not necessary when using the internal API, but a
must with libXrandr.

This only matters when using clones, which we do not accept yet. This
patch is for completeness and to avoid future surprises.

Return error if no CRTC.

Screen is a Xvnc thing and not relevant for x0vncserver etc.

RANDR is mandatory since Xorg 1.7, which is the oldest version we
support.

In RandR land, there's a lot of return code confusion. Our wrappers
are using the same return codes as RRCrtcSet, RRScreenSizeSet: 1/TRUE
for success. Fixes:

* vncRandRCreateOutputs did not follow this convention

* A lot of code returned -1 upon failure

* vncRandRDisableOutput returned 0 for already disabled outputs

These two code blocks are not specific to Xvnc/vnc.so, but useful for
x0vncserver as well. RandrGlue.h defines the interface on which
unixcommon depends on.

Compatibility with libXrandr, where the name is in dynamically
allocated XRROutputInfo.

Less confusing, and compatible with libXrandr.

Should use 2 spaces like the rest of the project.

The handler is for incoming data and we should not be abusing that
class for the writer class. Do proper write prototypes for the
relevant functions.

The previous code would incorrectly also add support for QEMU
key events if LED state was supported.

The VNC servers aren't great at getting full frames with each update,
so avoid calling it "frames per second" in the statistics as that
can be misleading.

Fixes issue #616

Shift key handling was improved in 30b3f92, but the test documentation
wasn't updated.

Improve AltGr detection even further on Windows so we can detect the
case when Ctrl and AltGr are pressed together.

Try to properly detect the fake CtrlL+AltR sequence Windows sends
when pressing AltGr. This allows us to send more accurate key
events over to the server.

It wasn't properly updated in 3112f50 when it was split off from
x0vncserver.cxx.

In XDesktop::start() we allocate pixel buffer and set it as the backend to the given VNCServer.
In XDesktop::stop() we deallocate the buffer, so we must unset it from the VNCServer as well.
Otherwise the VNCServer could try to access it and crash, for example in deferred update.

Originally calling VNCServertST::setPixelBuffer(PixelBuffer* pb_) with pb_=0 would do nothing.
With this change pb will be set to 0 and deferred update timer will be stopped.

Simple shifting can give noticable rounding errors if there is a large
difference in the number of bits between the formats. Do the proper
thing via a lookup table, the same way things are done for up conversion.

Bit shifting gives an approximate, but not properly accurate value
when upconverting. Do a proper calculation.

Colour map support was removed in b6b4dc6, but x0vncserver didn't
properly check if the X server required it.

Copy paste errors/brain fart:

 - Pixels do not need a factor 8 for any conversion

 - Multiplying bytes by 8 gives bits, so lower case 'b', and bits
   use SI prefixes, not IEC

TriFan and TriStrip were added in 1.12, so we need to have that code
conditional to support older versions of Xorg.

There were a bunch of parameters that weren't properly added to the
man pages when the features were added. Make sure everything is
properly in sync.

They share a lot of settings, so make sure the documentation is
identical in those cases.

The funcationality was removed in 6e49e95, so let's also clean up
the documentation referring to it.

Fl::arg accepts several arguments which we are not documenting. Also,
it accepts a -geometry argument, which clashes with our own -geometry
option.

We had overlooked a few so we didn't track all screen changes properly.

macOS no longer uses the old Aqua look, so tweak our things to fit
in better with the current state of things.

Menukey was broken by recent refactoring of OptionsDialog

Various errors exposed when connecting to RealVNC servers
on alternative platforms (ARM, SPARC).  SSLEngineManager
was also cleaned up but most of the changes are cosmetic.

XShmGetImage is much faster. On my machine, this reduces the CPU usage
of a fullscreen Youtube video playback from 40% to 25%.

Similar to 841e9f32d5 but for the
pointer. Fixes a problem where the desktop environment is unresponsive
(to the mouse) after fullscreen exit; Fixes #579.