Added index entries to make it easier to locate directory & file operations.

Doc/lib/libshutil.tex

@@ -9,6 +9,8 @@
 The \module{shutil} module offers a number of high-level operations on
 files and collections of files.  In particular, functions are provided 
 which support file copying and removal.
+\index{file!copying}
+\index{copying files}
 
 \strong{Caveat:}  On MacOS, the resource fork and other metadata are
 not used.  For file copies, this means that resources will be lost and 
@@ -58,6 +60,7 @@ file type and creator codes will not be correct.
 \end{funcdesc}
 
 \begin{funcdesc}{rmtree}{path\optional{, ignore_errors\optional{, onerror}}}
+\index{directory!deleting}
   Delete an entire directory tree.  If \var{ignore_errors} is true,
   errors will be ignored; if false or omitted, errors are handled by
   calling a handler specified by \var{onerror} or raise an exception.