- fixed botched code that did not actually complile in Win32


git-svn-id: svn://svn.code.sf.net/p/gwyddion/code/trunk/gwyddion@16655 25697fe4-d644-49b8-9d30-be5465f2adf3
- added GIF to known formats, seems writable at least on Win32


git-svn-id: svn://svn.code.sf.net/p/gwyddion/code/trunk/gwyddion@16656 25697fe4-d644-49b8-9d30-be5465f2adf3