Template sequence parameter and default value

[Andrey Zherikov]

What is the best way to emulate a default value for template 
sequence parameter of a function?

I want something like this:
```d
void foo(MODULES... = __MODULE__)() {}

// these should work:
foo!(module1, module2);
foo!(module1);
foo();          // this should use current module (__MODULE__) 
according to default value
```