* Track the line number of the current buffer position, so that error

* Track the line number of the current buffer position, so that error
  messages can refer to the line.  Change representation of buffer
  pointers to include the line number.  Add operation to generate a
  string that shows the line number and character number of either a
  given pointer or the current position.

* Eliminate DECREMENT-PARSER-BUFFER-POINTER, which was unused and
  makes implementing the line number more difficult.

* Add -NO-ADVANCE versions of procedures that match single characters.

* Change terminology: the index of the current character in the buffer
  is called a "position".  The word "pointer" is reserved to refer to
  pointer objects that are handed to the users, which themselves refer
  to positions.