All files in src/ apart from Rgeometry.c, Rgeometry.h, Rconvhulln.c,
Rdelaunayn.c Rtsearchn.c, Rtsearch_orig.c, Rtsearch.cpp,
RcppExports.cpp, Rinhulln.c, Rhalfspacen.c and geometry_init.c are
taken from or based on Qhull (http://www.qhull.org/), and covered by
COPYING.txt.
