Add qhull source code and license file

extern/qhull/COPYING.txt

@@ -0,0 +1,38 @@
+ Qhull, Copyright (c) 1993-2012
+
+ C.B. Barber
+ Arlington, MA
+
+ and
+
+ The National Science and Technology Research Center for
+ Computation and Visualization of Geometric Structures
+ (The Geometry Center)
+ University of Minnesota
+
+ email: [email protected]
+
+This software includes Qhull from C.B. Barber and The Geometry Center.
+Qhull is copyrighted as noted above. Qhull is free software and may
+be obtained via http from www.qhull.org. It may be freely copied, modified,
+and redistributed under the following conditions:
+
+1. All copyright notices must remain intact in all files.
+
+2. A copy of this text file must be distributed along with any copies
+ of Qhull that you redistribute; this includes copies that you have
+ modified, or copies of programs or other software products that
+ include Qhull.
+
+3. If you modify Qhull, you must include a notice giving the
+ name of the person performing the modification, the date of
+ modification, and the reason for such modification.
+
+4. When distributing modified versions of Qhull, or other software
+ products that include Qhull, you must provide notice that the original
+ source code may be obtained as noted above.
+
+5. There is no warranty or other guarantee of fitness for Qhull, it is
+ provided solely "as is". Bug reports or fixes may be sent to
+ [email protected]; the authors may or may not act on them as
+ they desire.