COMP: On MacOSX, waiting issue #3741 is *really* solved uses VTK 5.10

It turns out that the test build I initiated managed to go way beyond
the original stopping point [See r23344]. That said, there are still
the same issue when building SubjectHierarchy, Annotations module ...

This commits reverts back to VTK 5.10 for MacOSX.

The solution gonna be to continue the work initiated in [1] and
remove the top level call to "find_package()" and instead have
every Slicer libraries/modules including his set of direct dependencies.

[1] http://massmail.spl.harvard.edu/public-archives/slicer-devel/2014/015671.html

git-svn-id: http://svn.slicer.org/Slicer4/trunk@23353 3bd1e089-480b-0410-8dfb-8563597acbee