Allow static variables in range expressions

[jdm]

static foo: int = 16;

fn main() {
    match 15 {
        3 .. foo => io::println(~"success"),
        _ => fail!()
    }
}

/tmp/rusttest.rs:5:13: 5:16 error: unexpected token: `foo`
/tmp/rusttest.rs:5         3 .. foo => io::println(~"success"),
                                ^~~

[jdm]

I'm surprised that #6245 didn't make this work.

[emberian]

Closing as a dupe of #7222