In apollopanstitcher, fixed a bug that caused this program to produce...

In apollopanstitcher, fixed a bug that caused this program to produce erroneous outputs a small percentage of the times it was run (less than 3% failure rate). The bad outputs looked valid - visually - but the stitching was incorrect (pixels would be in the wrong place). This was a general failure, not caused by a particular input or set of parameter values. Fixes #1053.

git-svn-id: http://subversion.wr.usgs.gov/repos/prog/isis3/trunk@4935 41f8697f-d340-4b68-9986-7bafba869bb8