Usage: FSEEK <filenum> <offset> <whence>
  Moves the current position in an open file stream.
  Supported values for whence are:
    SEEK_SET  offset plus beginning of file
    SEEK_CUR  offset plus current position
    SEEK_END  offset plus end of file

See also:
  ALIAS FUNCTIONS
  FCLOSE
  FWRITE
  FWRITELN
  FPUTC
