cgal/Modifier/doc_tex/Modifier

The .gif figures are needed for the Modifier section. Since
the modifier section does reside in a different directory, but
does not create its own file, for example, for a chapter, will the
latex_to_html converter not find the gif file automatically from the
Modifier directory. The latex_to_html converter searches the file in
the Miscellany directory instead, where we just keep a copy of those
gif files for now, until maybe the converter can be improved.