Add feature flag to reference docs for RFC 1623.
@@ -1376,7 +1376,7 @@ unsafe fn bump_levels_unsafe2() -> u32 {
Mutable statics have the same restrictions as normal statics, except that the
type of the value is not required to ascribe to `Sync`.
-#### `'static` lifetime elision
+#### `'static` lifetime elision [unstable]
Both constant and static declarations of reference types have *implicit*
`'static` lifetimes unless an explicit lifetime is specified. As such, the
@@ -1384,6 +1384,7 @@ constant declarations involving `'static` above may be written without the
lifetimes. Returning to our previous example:
```rust
+#[feature(static_in_const)]
const BIT1: u32 = 1 << 0;
const BIT2: u32 = 1 << 1;
