FSplit procedure

  DECLARATION:  FSplit(Path : PathStr; var Dir: DirStr;
                       var Name : NameStr; var Ext : ExtStr)

      PURPOSE:  Splits a filename into its three components

         UNIT:  System

      REMARKS:  This splits a complete filename specified by Path, into
                Dir, indicating the drive and directory, Name, indicating
                the file name, and Ext, indicating the file extension
                including the preceeding dot.

                FSplit never adds or removes characters.  The concatenation
                of the resulting Dir, Name and Ext will always equal Path.

                The PathStr, DirStr, NameStr, and ExtStr types are defined
                in the DOS unit as follows:

                          Type
                             PathStr = String[79];
                             DirStr  = String[67];
                             NameStr = String[8];
                             ExtStr  = String[4];