[geometry] Add basic draft of the Robustness topic for docs

git-svn-id: http://svn.boost.org/svn/boost/trunk@86434 b8fc166d-592f-0410-95f2-cb63ce0dd405
[geometry] Add TODO items

git-svn-id: http://svn.boost.org/svn/boost/trunk@86435 b8fc166d-592f-0410-95f2-cb63ce0dd405
[geometry] Add TODO item on doxygen_d_robustness.hpp

git-svn-id: http://svn.boost.org/svn/boost/trunk@86436 b8fc166d-592f-0410-95f2-cb63ce0dd405
[geometry] Add TODO item EGC

git-svn-id: http://svn.boost.org/svn/boost/trunk@86437 b8fc166d-592f-0410-95f2-cb63ce0dd405