- renamed merge type "Smooth" to "Average" because that's what it does (keeping
  the integer enum id)
- added a new merge type "Interpolation" which should be actually smooth


git-svn-id: svn://svn.code.sf.net/p/gwyddion/code/trunk/gwyddion@16827 25697fe4-d644-49b8-9d30-be5465f2adf3
- some more 2.40 news


git-svn-id: svn://svn.code.sf.net/p/gwyddion/code/trunk/gwyddion@16828 25697fe4-d644-49b8-9d30-be5465f2adf3