Make sure we check that PixelFormats we get are actually valid.
Converting to RGB might involve a precision increase

Need to do more than a simple shift to get the appropriate
new value. This isn't quite as exact as a proper multiplication
and division, but the error is so small it's not worth the
extra cycles.
Check that we have a cursor to restore

Forgot to check that we actually have a cursor from the server
before trying to switch back to it after dismissing the context menu.
Support keeping libjpeg's default compression setting
Reduce dependencies on TransImageGetter.h
Clean up header dependencies in the vncviewer directory
Remove unsused, commented out code
Remove unused pixel conversion method
Remove unused alternative code path from the ZRLE and Hextile decoders
Remove unused (and commented out) PixelBuffer::getPixel()
Remove the scaled pixel buffer classes as they are not used.

There were also reports of them being broken last time we still
made use of them.
Remove all unused TX widgets
Remove unused method prototype
Get rid of unused things in the ZRLE encoder

Get rid of unused shared MemOutStream and variable max length
functionality in the ZRLE encoder.
Document the different pixel representations that we deal with
Be more consistent in referring to pixel byte streams as buffers
Get rid of the register mechanism for encoders and decoders

We have no use for it, so let's keep things simple.
Stop storing a copy of the encodings as we don't use it for anything
Add some missing whitespace
Remove some premature optimisation

Reduces header dependencies.