From Pere:
fixes  bugs #101047 and bug #101049 to keep CMake with latest changes in trunk.


git-svn-id: https://root.cern.ch/svn/root/trunk@49130 27541ba8-7e3a-0410-8455-c3a389f83636
From Pere:
fixes Jira issue ROOT-183  and some minor change on FindGraphvix.cmake.


git-svn-id: https://root.cern.ch/svn/root/trunk@49132 27541ba8-7e3a-0410-8455-c3a389f83636
add a flag in Sumw2() to delete error array structure


git-svn-id: https://root.cern.ch/svn/root/trunk@49133 27541ba8-7e3a-0410-8455-c3a389f83636