fExtension()

         Returns the extension of a file

    Syntax:

         fExtension ( cFile ) -> cExtension

         cFile : The name of the file

    Description:

         Returns the file extension following the DOS rule for description,
         that is to say, a name of 8 letters followed by a point and an
         extension of 3 letters.

    Return:

         File extension as a character value or "" if file not exists

    Example:

         ? fExtensi.n ( "C:\FastLib\Fast.Txt" ) // Txt