extern and opaque structs

[James Miller]

I'm doing C bindings and I have an opaque struct and an extern'd 
variable of the type of that struct. The problem is that dmd is 
complaining that the struct has no definition (which is true). 
Making it a pointer works (expected) but i can't do that because 
the interface is expecting an full struct.

Adding __gshared doesn't help.
I assume this is bug, since usage of extern means that I don't 
need to know the size, since it will be allocated in the C code, 
not the D code.

--
James Miller