Added note about installing libxt-dev (VTK 5.2 bombs badly if this is not present during build).
Added note about installing libxt-dev (VTK 5.2 bombs badly if this is
not present during build).

codester2/devide.johannes,fvpolpeta/devide.johannes,nagyistoce/devide.johannes,ivoflipse/devide.johannes,codester2/devide.johannes,nagyistoce/devide.johannes,ivoflipse/devide.johannes,chrisidefix/devide.johannes,fvpolpeta/devide.johannes,chrisidefix/devide.johannes