calling dll native entry point for mixed assemblies

[Vincent Povirk]

> Shouldn't I add flag to winnt.h in a separate patch?
> The change I made to FixupVTable is for avoiding calling times
> assembly_from_hmodule twice when called from _CorDllMain (which involves
> extra heap allocation/free). If you think it is not an issue I can
> simplify the patch and do not touch FixupVTable. Or change FixupVTable
> as first part, then the main change as the next part.

Ah, that makes sense now. I missed what you were doing with
FixupVTable. I don't think parsing the header multiple times is a
problem, but it also makes sense this way.

I think I've seen header changes done both ways.