Better to check the actual list of supported encodings directly.
Makes parts more readable, and no risk of getting out of sync.

No need to spread things out. Keep all of the handling in a single
place to make things clearer.

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.

Loosen the definition of "lossless" a bit so that we can use high
quality JPEG to refresh damaged parts of the screen. Although this
isn't bit perfect, it is close enough that most users will not be
able to tell the difference.

Level 9 is used rather than level 8 because some monitors have
exaggerated contrast that allows the artefacts from level 8 to be
noticeable.

The update size is in bytes, but we are counting pixels. So make
sure we convert things properly before comparing.

If an area recently changed then we can guess that it will most likely
change again very soon. In such a case it is meaningless to send a
lossless refresh as it will directly be overwritten. Keep track of
such areas and avoid refreshing them until we no longer see any
changes to them.

We don't want to waste bandwidth on the lossless refresh if we might
need that bandwidth for a normal update. Try to estimate how much
data we can safely send without interfering.

Resend pixel perfect copies of areas that were previously sent
using a lossy encoder. This is done when there is no normal update
to send, and no congestion.

We already have an assignment operator, so no need for this method.

We cannot send updates for a cursor that is outside the requested
region, so make sure we track things properly. This also has the nice
side effect of just re-sending the bits needed when the cursor overlaps
a changed part of the framebuffer.

Also avoids %lld which isn't supported on Windows.

Either by casting, or switching to a more appropriate type
for the variable.

The previous FIXME was incorrect. The old code did in fact continue
looking over the entire area. This commit restores that old behaviour.

It knows more details so it can track things better.

Having it in ConnParams made the linker pull all the encoder objects
into vncviewer, making it larger than necessary and giving it extra
parameters in its help output that weren't relevant.

This allows us to apply a lot more server logic
independently of which encoder is in use.

Most of this class are things moved over from the
Tight encoder.