support UFCS with fully qualified function names

[bearophile]

Timothee Cour:

> I'd like to be able to use UFCS with fully qualified function 
> names.

>     auto a="".(std.path.join)("\n");

It seems an acceptably-looking syntax. But maybe D.learn is not 
the best place to discuss new D syntax.

Regarding new UFCS-related syntax, I sometimes wish for:

alias T = foo.typeof;
byBoolVal.assert;

http://d.puremagic.com/issues/show_bug.cgi?id=4272

Bye,
bearophile