librustc: Always parse macro!()/macro![] as expressions if not

followed by a semicolon.

This allows code like `vec![1i, 2, 3].len();` to work.

This breaks code that uses macros as statements without putting
semicolons after them, such as:

    fn main() {
        ...
        assert!(a == b)
        assert!(c == d)
        println(...);
    }

It also breaks code that uses macros as items without semicolons:

    local_data_key!(foo)

    fn main() {
        println("hello world")
    }

Add semicolons to fix this code. Those two examples can be fixed as
follows:

    fn main() {
        ...
        assert!(a == b);
        assert!(c == d);
        println(...);
    }

    local_data_key!(foo);

    fn main() {
        println("hello world")
    }

RFC #378.

Closes #18635.

[breaking-change]

src/libstd/io/stdio.rs

@@ -95,9 +95,11 @@ fn src<T, F>(fd: libc::c_int, _readable: bool, f: F) -> T where
     }
 }
 
-thread_local!(static LOCAL_STDOUT: RefCell<Option<Box<Writer + Send>>> = {
-    RefCell::new(None)
-})
+thread_local! {
+    static LOCAL_STDOUT: RefCell<Option<Box<Writer + Send>>> = {
+        RefCell::new(None)
+    }
+}
 
 /// A synchronized wrapper around a buffered reader from stdin
 #[deriving(Clone)]