ZoomTool.h: 2011-09-28 Steven Lambright - Removed p_userCursor. It was only...

ZoomTool.h: 2011-09-28 Steven Lambright - Removed p_userCursor. It was only causing bugs. As a result, the mouseButtonRelease method did nothing so I removed that too. Zooming happens on the rubberBandComplete slot. Fixes #505

git-svn-id: http://subversion.wr.usgs.gov/repos/prog/isis3/trunk@3323 41f8697f-d340-4b68-9986-7bafba869bb8