Add a missing header in vtkCompositePolyDataMapper2

For builds using VS2012, <algorithm> needs to be included in
order to use std::max.

Change-Id: Ia100caf9c08d7357890014e990d162cc32981d2b
Signed-off-by: Andrew Maclean <andrew.amaclean@gmail.com>
Merge topic 'fix_missing_header' into master

b0f0948f Add a missing header in vtkCompositePolyDataMapper2