(1) Catch exception thrown in 2D case.
(2) Fixed DESCRIPTION file.
(3) After deleting pcell, explicitly set pcell to 0. Some compilers may not do this.

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/ptinpoly@27 edb9625f-4e0d-4859-8d74-9fd3b1da38cb