I noticed quotient, remainder and modulo don't actually say how they
round.  The change below is what R5RS specifies, and what guile
already does, if I'm not mistaken.

	* scheme-data.texi (Integer Operations): Describe how quotient,
	remainder, and modulo round their results.

For ease of reading, the new text would be:

 - Scheme Procedure: quotient n d
 - Scheme Procedure: remainder n d
     Return the quotient or remainder from N divided by D.  The
     quotient is rounded towards zero, and the remainder will have the
     same sign as N.  In all cases quotient and remainder satisfy N =
     Q*D + R.

          (remainder 13 4) => 1
          (remainder -13 4) => -1

 - Scheme Procedure: modulo n d
     Return the remainder from N divided by D, with the same sign as D.

          (modulo 13 4) => 1
          (modulo -13 4) => 3
          (modulo 13 -4) => -1
          (modulo -13 -4) => -3