Attempt to clarify removedirs().

Based on SF bug #574773.

Doc/lib/libos.tex

@@ -750,7 +750,7 @@ Availability: Macintosh, \UNIX, Windows.
 
 \begin{funcdesc}{removedirs}{path}
 \index{directory!deleting}
-Recursive directory removal function.  Works like
+Removes directories recursively.  Works like
 \function{rmdir()} except that, if the leaf directory is
 successfully removed, directories corresponding to rightmost path
 segments will be pruned way until either the whole path is consumed or