Since we started using ctors, there was no way to do this since by the time main() runs it's already too late.

So here's an idea: we could come up with some symbol name like 'g_get_slice_allocator_config()' or something, and dlsym() that out of the process on libglib startup.  If the user provides that function, we call it to determine what our configuration should be.

I think it's probably good to continue to allow this (and Mozilla, for example, is quite upset to see it gone).  I also can't think of a better way to do it...

Thoughts?