More code clean-up and minor improvements.

   cdftest.R
   interact.R
   Kmeasure.R
   morphology.R
   pppmatch.R [thanks to Dominic Schuhmacher]
   psst.R
   psstA.R
   psstG.R
   quadratcount.R
   quadrattest.R
   random.R
   residppm.R
   rhohat.R
   rho2hat.R
   rPerfect.R
   simplepanel.R
   slrm.R
   smooth.ppp.R
   summary.im.R
   summary.ppm.R
   superimpose.R
   tess.R
   Tstat.R
   wingeom.R
     Removed variables which are identified as 'unused' by codetools

   slrm.R
     Output now conforms to options('width')

   unique.ppp.R
   ppx.R
   duplicated.ppp.Rd
      New functions anyDuplicated.ppp and anyDuplicated.ppx

   ppp.R
      Faster check for duplicated points (suggested by Maxime Woringer)

   NEWS
   DESCRIPTION
   spatstat-package.Rd
      updated, acknowledged Dominic Schuhmacher and Maxime Woringer.