I tried the package on the debian site as well, and got the same errors.
Try the package from
http://www.realvnc.com (
http://fresh.t-systems-sfr.com/linux...unixsrc.tar.gz for a quick link to wget). I was able to download, compile, and run that in my development environment. It includes the viewer and the server.
And to answer your original question, I believe it is looking for the Toggle.h file. You may have to download some X11 sources to build that package.