Remove \platform declaration; this module is generic.

Doc/lib/libstat.tex

@@ -2,7 +2,6 @@
          Interpreting \function{stat()} results}
 
 \declaremodule{standard}{stat}
-  \platform{Unix, Windows}
 \modulesynopsis{Utilities for interpreting the results of
   \function{os.stat()}, \function{os.lstat()} and \function{os.fstat()}.}
 \sectionauthor{Skip Montanaro}{skip@automatrix.com}