Since 53f913a we initialize the underlying PixelBuffer with 0x0
dimensions, which means we need to keep more explicit track of what
we are trying to allocate in the setup methods.

This will allow us to render more things than just the framebuffer.

The complex logic waiting for events didn't result in any added
performance, so use the simpler approach.

We need to make sure the display server has finished reading our
previous update before we overwrite the buffer with the next update.

The damage tracking region needs to be protected from multiple
threads accessing it at once. The rest should be fine though.

This avoid a lot of unnecessary middle men. This also pushes the
responsibility for pixel format conversion into the encoders and
decoders. The new bufferFromBuffer() is used for direct conversion,
rather than PixelTransformer/TransImageGetter.

It was confusing and not properly used everywhere.
Callers should use the stride they get when they get
the buffer pointer.

This allows us to gracefully fall back to the FLTK code in case the
platform specific code cannot be used.

git-svn-id: svn://svn.code.sf.net/p/tigervnc/code/trunk@4492 3789f03b-4d11-0410-bbf8-ca57d06f2519