Added error checks to several scanf(...) and read(...) calls due to the...

Added error checks to several scanf(...) and read(...) calls due to the compiler warnings that cropped up on prog3 because return values were being ignored.

git-svn-id: http://subversion.wr.usgs.gov/repos/prog/isis3/trunk@2651 41f8697f-d340-4b68-9986-7bafba869bb8