Begin experimental support for pin reborrowing · qinheping/verify-rust-std@56704d4

Original file line number	Diff line number	Diff line change
`@@ -1408,6 +1408,7 @@ impl<Ptr: DerefMut> Pin<Ptr> {`
`1408`	`1408`	`/// }`
`1409`	`1409`	`/// }`
`1410`	`1410`	/// ```
	`1411`	`+ #[cfg_attr(not(bootstrap), lang = "pin_as_mut")]`
`1411`	`1412`	`#[stable(feature = "pin", since = "1.33.0")]`
`1412`	`1413`	`#[inline(always)]`
`1413`	`1414`	`pub fn as_mut(&mut self) -> Pin<&mut Ptr::Target> {`