Backport libs stabilizations to 1.21 beta

This includes the following stabilizations:

- tcpstream_connect_timeout #44563
- iterator_for_each #44567
- ord_max_min #44593
- compiler_fences #44595
- needs_drop #44639
- vec_splice #44640

Author: dtolnay

src/liballoc/vec.rs

@@ -1950,7 +1950,7 @@ impl<T> Vec<T> {
     /// assert_eq!(u, &[1, 2]);
     /// ```
     #[inline]
-    #[stable(feature = "vec_splice", since = "1.22.0")]
+    #[stable(feature = "vec_splice", since = "1.21.0")]
     pub fn splice<R, I>(&mut self, range: R, replace_with: I) -> Splice<I::IntoIter>
         where R: RangeArgument<usize>, I: IntoIterator<Item=T>
     {
@@ -2553,13 +2553,13 @@ impl<'a, T> InPlace<T> for PlaceBack<'a, T> {
 /// [`splice()`]: struct.Vec.html#method.splice
 /// [`Vec`]: struct.Vec.html
 #[derive(Debug)]
-#[stable(feature = "vec_splice", since = "1.22.0")]
+#[stable(feature = "vec_splice", since = "1.21.0")]
 pub struct Splice<'a, I: Iterator + 'a> {
     drain: Drain<'a, I::Item>,
     replace_with: I,
 }
 
-#[stable(feature = "vec_splice", since = "1.22.0")]
+#[stable(feature = "vec_splice", since = "1.21.0")]
 impl<'a, I: Iterator> Iterator for Splice<'a, I> {
     type Item = I::Item;
 
@@ -2572,18 +2572,18 @@ impl<'a, I: Iterator> Iterator for Splice<'a, I> {
     }
 }
 
-#[stable(feature = "vec_splice", since = "1.22.0")]
+#[stable(feature = "vec_splice", since = "1.21.0")]
 impl<'a, I: Iterator> DoubleEndedIterator for Splice<'a, I> {
     fn next_back(&mut self) -> Option<Self::Item> {
         self.drain.next_back()
     }
 }
 
-#[stable(feature = "vec_splice", since = "1.22.0")]
+#[stable(feature = "vec_splice", since = "1.21.0")]
 impl<'a, I: Iterator> ExactSizeIterator for Splice<'a, I> {}
 
 
-#[stable(feature = "vec_splice", since = "1.22.0")]
+#[stable(feature = "vec_splice", since = "1.21.0")]
 impl<'a, I: Iterator> Drop for Splice<'a, I> {
     fn drop(&mut self) {
         // exhaust drain first

src/libcore/cmp.rs

@@ -456,7 +456,7 @@ pub trait Ord: Eq + PartialOrd<Self> {
     /// assert_eq!(2, 1.max(2));
     /// assert_eq!(2, 2.max(2));
     /// ```
-    #[stable(feature = "ord_max_min", since = "1.22.0")]
+    #[stable(feature = "ord_max_min", since = "1.21.0")]
     fn max(self, other: Self) -> Self
     where Self: Sized {
         if other >= self { other } else { self }
@@ -472,7 +472,7 @@ pub trait Ord: Eq + PartialOrd<Self> {
     /// assert_eq!(1, 1.min(2));
     /// assert_eq!(2, 2.min(2));
     /// ```
-    #[stable(feature = "ord_max_min", since = "1.22.0")]
+    #[stable(feature = "ord_max_min", since = "1.21.0")]
     fn min(self, other: Self) -> Self
     where Self: Sized {
         if self <= other { self } else { other }

src/libcore/iter/iterator.rs

@@ -518,7 +518,7 @@ pub trait Iterator {
     ///       .for_each(|(i, x)| println!("{}:{}", i, x));
     /// ```
     #[inline]
-    #[stable(feature = "iterator_for_each", since = "1.22.0")]
+    #[stable(feature = "iterator_for_each", since = "1.21.0")]
     fn for_each<F>(self, mut f: F) where
         Self: Sized, F: FnMut(Self::Item),
     {

src/libcore/mem.rs

@@ -402,7 +402,7 @@ pub fn align_of_val<T: ?Sized>(val: &T) -> usize {
 /// }
 /// ```
 #[inline]
-#[stable(feature = "needs_drop", since = "1.22.0")]
+#[stable(feature = "needs_drop", since = "1.21.0")]
 pub fn needs_drop<T>() -> bool {
     unsafe { intrinsics::needs_drop::<T>() }
 }

src/libcore/sync/atomic.rs

@@ -1752,7 +1752,7 @@ pub fn fence(order: Ordering) {
 /// [`Relaxed`]: enum.Ordering.html#variant.Relaxed
 /// [memory barriers]: https://www.kernel.org/doc/Documentation/memory-barriers.txt
 #[inline]
-#[stable(feature = "compiler_fences", since = "1.22.0")]
+#[stable(feature = "compiler_fences", since = "1.21.0")]
 pub fn compiler_fence(order: Ordering) {
     unsafe {
         match order {

src/libstd/net/tcp.rs

@@ -167,7 +167,7 @@ impl TcpStream {
     /// connection request.
     ///
     /// [`SocketAddr`]: ../../std/net/enum.SocketAddr.html
-    #[stable(feature = "tcpstream_connect_timeout", since = "1.22.0")]
+    #[stable(feature = "tcpstream_connect_timeout", since = "1.21.0")]
     pub fn connect_timeout(addr: &SocketAddr, timeout: Duration) -> io::Result<TcpStream> {
         net_imp::TcpStream::connect_timeout(addr, timeout).map(TcpStream)
     }