vcl: assert more useful truths on BitmapWriterAccess completion.
vcl: assert more useful truths on BitmapWriterAccess completion.

Change-Id: I2ccc5eb64bf3b5d5ce94e2ddd4b9b458c3eda217

Conflicts:
	vcl/opengl/salbmp.cxx

JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core