[vtk-developers] Modified() modified

[John Biddiscombe]

I've added a ModifiedEvent to vtkCallback and also noticed a discrepancy 
between some of the macros in vtkSetGet.h

For consistency, they all now
SetData first
Call Modified() afterwards

previously some were doing
Call Modified() first
SetData afterwards

I'll check this in soon, but it is a fairly fundamental change and might 
affect someone. Please warn me if you think it will. (I won't check this in 
until the dashboard stabilizes from Berk's stuff).

JB