Reverted cnetcombinept Makefile to standard file (removed -frounding-math)....

Reverted cnetcombinept Makefile to standard file (removed -frounding-math). Fixes clang warning on prog17 about unsupported compile flag.

git-svn-id: http://subversion.wr.usgs.gov/repos/prog/isis3/trunk@7283 41f8697f-d340-4b68-9986-7bafba869bb8