[GSOC] Database API

[Kagamin]

Robert Jacques Wrote:

> > Should be Algebraic!(T, void). If that doesn't currently compile, we  
> > should make it compile.
> >
> > Andrei
> 
> For what it's worth, both Algebraic!(T, void*) and Algebraic!(T, void)  
> compile on my branch of std.variant.

can't assign null

	alias Algebraic!(int,void) nint;
	nint n1=5;
	assert(n1==5);
	n1=null;

\std\variant.d:497: Error: static assert  "Cannot store a void* in a VariantN!(maxSize,int,void). Valid types are (int, void)"
test.d:45:        instantiated from here: opAssign!(void*)