C style callbacks fix for member callbacks

[IntegratedDimensions]

Investigating further, this does not seem to be pushed on the 
stack but set in EAX.

Hence no amount of parameter placement manipulation will work. It 
actually becomes an easy situation although this will be invalid 
as it will be be whatever value is in EAX used by the caller.

One cannot set this directly though but one does not have to use 
it. Therefor, simply using a member function here is the same as 
a static and no changes have to be made. Quite an easy fix. I do 
not know how safe it is. The docs say this is pushed and that is 
probably generally true.