Fix documentation for QSGGeometry::allocate()
Fix documentation for QSGGeometry::allocate()

Make clear in the documentation that client code must dirty the
geometry node that contains the geometry class, to allow the
renderer implementation to update internal buffers.

Change-Id: I5cfddee1d0969410d7b3175c381679bd9083cc2b
Reviewed-by: Damian Jansen <7096c146b6657747707fd6f239957394d7247180@nokia.com>
Reviewed-by: Alex Wilson <75fe28a89a52dd8f665f8aed10f0a66d41b4f1d0@nokia.com>

qmlc/qtdeclarative,crobertd/qtdeclarative,corngood/qtdeclarative,corngood/qtdeclarative,jfaust/qtdeclarative,matthewvogt/qtdeclarative,corngood/qtdeclarative,matthewvogt/qtdeclarative,mgrunditz/qtdeclarative-2d,matthewvogt/qtdeclarative,corngood/qtdeclarative,qmlc/qtdeclarative,corngood/qtdeclarative,mgrunditz/qtdeclarative-2d,matthewvogt/qtdeclarative,mgrunditz/qtdeclarative-2d,qmlc/qtdeclarative,qmlc/qtdeclarative,matthewvogt/qtdeclarative,mgrunditz/qtdeclarative-2d,matthewvogt/qtdeclarative,jfaust/qtdeclarative,matthewvogt/qtdeclarative,crobertd/qtdeclarative,matthewvogt/qtdeclarative,qmlc/qtdeclarative,jfaust/qtdeclarative,qmlc/qtdeclarative,jfaust/qtdeclarative,corngood/qtdeclarative,jfaust/qtdeclarative,jfaust/qtdeclarative,qmlc/qtdeclarative,corngood/qtdeclarative,mgrunditz/qtdeclarative-2d,jfaust/qtdeclarative,qmlc/qtdeclarative,crobertd/qtdeclarative,crobertd/qtdeclarative,crobertd/qtdeclarative,crobertd/qtdeclarative,crobertd/qtdeclarative,mgrunditz/qtdeclarative-2d,mgrunditz/qtdeclarative-2d