Tweak the scaling() comment


git-svn-id: http://seriss.com/public/fltk/fltk/branches/branch-1.3@10269 ea41ed52-d2ee-0310-a9c1-e6b18d33e121
Small fix in the bilinear formula

After consulting Gimp again, the formula was missing a final divide. This
takes care of the 1:1 discrepancy.


git-svn-id: http://seriss.com/public/fltk/fltk/branches/branch-1.3@10270 ea41ed52-d2ee-0310-a9c1-e6b18d33e121