Sort out canvas window events. Remove confusing feature callbacks. Add enter/leave calbacks. Make window copy do canvas duplication properly. Remove Robs cached position data because its error prone.

these files are part of an old version of zmap which was embedded in xace, they have been archived within cvs.

tidy up callback prototypes which were all to cock. Add keyboard short cuts and in so doing fix keyboard focus bug. Add visibility change callback for when zoom or window position is changed.