+Move MARKER to position POSITION in BUFFER.
+POSITION can be a marker, an integer or nil. If POSITION is an
+integer, make MARKER point before the POSITIONth character in BUFFER.
+If POSITION is nil, makes MARKER point nowhere. Then it no longer
+slows down editing in any buffer. If POSITION is less than 1, move
+MARKER to the beginning of BUFFER. If POSITION is greater than the
+size of BUFFER, move MARKER to the end of BUFFER.