struct initializer

[Dom DiSc via Digitalmars-d-learn]

```d
struct S { int a; int b; }

S s = { 5, 2 }; // works fine
S fun() { return { 5, 2 }; } // doesn't work :-(

S fun2() { S s = { 5, 2 }; return s; } // works but is ugly

struct S2 { int a; int b; this(int c, int d) { a=c; b=d; } }

S2 fun3() { return S2( 5, 2 ); } // works but requires explicit 
constructor
```

Is there a reason why the short form is not possible?
It's clearly an initialization of a new instance of a struct, and 
the requested type is unambigous (the return type of the 
function).