More accurate spans, season 3

[sanxiyn]

No description provided.

[sanxiyn]

Given

fn f(_: &int) {}
fn g(x: int) -> int { x }
fn main() {
    let v = ~[0];
    f(~g(0));
    f(~v[0]);
}

Before:

span.rs:5     f(~g(0));
                ^~~~~~
span.rs:6     f(~v[0]);
                ^~~~

After:

span.rs:5     f(~g(0));
                ^~~~~
span.rs:6     f(~v[0]);
                ^~~~~

That is, ExprCall had one token more, and ExprIndex had one token less.

[brson]

Way to pay attention to detail, @sanxiyn!