Update QHull to version 8.0.0

Note: deactivated qhull tests and install.

thirdparty/qhull/Announce.txt

@@ -1,7 +1,8 @@
 
- Qhull 2015.2  2016/01/18
+ Qhull 2020.1  2020/05/29
 
         http://www.qhull.org
+        http://github.com/qhull/qhull/wiki
         git@github.com:qhull/qhull.git
         http://www.geomview.org
 
@@ -16,16 +17,17 @@ input transformations, randomization, tracing, multiple output formats, and
 execution statistics.  The program can be called from within your application.
 You can view the results in 2-d, 3-d and 4-d with Geomview.
 
-To download Qhull:
+Download Qhull:
+
         http://www.qhull.org/download
         git@github.com:qhull/qhull.git
 
-Download qhull-96.ps for:
+Reference:
 
         Barber, C. B., D.P. Dobkin, and H.T. Huhdanpaa, "The
         Quickhull Algorithm for Convex Hulls," ACM Trans. on
         Mathematical Software, 22(4):469-483, Dec. 1996.
-        http://www.acm.org/pubs/citations/journals/toms/1996-22-4/p469-barber/
+        http://portal.acm.org/citation.cfm?doid=235815.235821
         http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.117.405
 
 Abstract: