Minor extension to cast syntax

[Gregor Richards]

Blech. Makes it look like you're calling a function with arguments being 
a type and then some expression. The current syntax is more similar to 
calling a templated cast function:

cast(int)(foo)
cast!(int)(foo)

That is, cast is a function with a template parameter of the type you're 
casting it to. This isn't how it's implemented at all of course, but the 
syntax is reminiscent of that, and I think that's the better analogy.

  - Gregor Richards