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.