It seems that _HAS_ITERATOR_DEBUGGING affects the layout of some
classes, which of course means horrible breakage if some of the source
files are compiled with it, the rest not.

http://msdn.microsoft.com/en-us/library/aa985939%28v=vs.80%29.aspx
http://connect.microsoft.com/VisualStudio/feedback/details/334315/has-iterator-debugging-0-causes-crash

I will just have to fix the code in this handful of source files so
that it compiles with _DEBUG defined. If I can be bothered.