Bugfixes and a new dataset.

   relrisk.R
	Two bug fixes: (1) handling of character 'case';
        (2) handling of numerical errors eg probabilities of -2e-16.

   plot.ppp.R
	Bug fix: warned of NA's amongst the marks, even if there were no NA's
	in the column(s) selected by which.marks.

   bdspots.rda [New file]
   bdspots.Rd [New file]
      New dataset.

   NEWS
   DESCRIPTION
   spatstat-package.Rd
	updated. Acknowledged Enrique Miranda.