Update issue number of shrink_to methods to point the tracking issue

Author: ordovicia

src/liballoc/collections/binary_heap.rs

@@ -529,7 +529,7 @@ impl<T: Ord> BinaryHeap<T> {
     /// assert!(heap.capacity() >= 10);
     /// ```
     #[inline]
-    #[unstable(feature = "shrink_to", reason = "new API", issue="0")]
+    #[unstable(feature = "shrink_to", reason = "new API", issue="56431")]
     pub fn shrink_to(&mut self, min_capacity: usize) {
         self.data.shrink_to(min_capacity)
     }

src/liballoc/collections/vec_deque.rs

@@ -701,7 +701,7 @@ impl<T> VecDeque<T> {
     /// buf.shrink_to(0);
     /// assert!(buf.capacity() >= 4);
     /// ```
-    #[unstable(feature = "shrink_to", reason = "new API", issue="0")]
+    #[unstable(feature = "shrink_to", reason = "new API", issue="56431")]
     pub fn shrink_to(&mut self, min_capacity: usize) {
         assert!(self.capacity() >= min_capacity, "Tried to shrink to a larger capacity");
 

src/liballoc/string.rs

@@ -1050,7 +1050,7 @@ impl String {
     /// assert!(s.capacity() >= 3);
     /// ```
     #[inline]
-    #[unstable(feature = "shrink_to", reason = "new API", issue="0")]
+    #[unstable(feature = "shrink_to", reason = "new API", issue="56431")]
     pub fn shrink_to(&mut self, min_capacity: usize) {
         self.vec.shrink_to(min_capacity)
     }

src/liballoc/vec.rs

@@ -613,7 +613,7 @@ impl<T> Vec<T> {
     /// vec.shrink_to(0);
     /// assert!(vec.capacity() >= 3);
     /// ```
-    #[unstable(feature = "shrink_to", reason = "new API", issue="0")]
+    #[unstable(feature = "shrink_to", reason = "new API", issue="56431")]
     pub fn shrink_to(&mut self, min_capacity: usize) {
         self.buf.shrink_to_fit(cmp::max(self.len, min_capacity));
     }

src/libstd/collections/hash/map.rs

@@ -1018,7 +1018,7 @@ impl<K, V, S> HashMap<K, V, S>
     /// map.shrink_to(0);
     /// assert!(map.capacity() >= 2);
     /// ```
-    #[unstable(feature = "shrink_to", reason = "new API", issue="0")]
+    #[unstable(feature = "shrink_to", reason = "new API", issue="56431")]
     pub fn shrink_to(&mut self, min_capacity: usize) {
         assert!(self.capacity() >= min_capacity, "Tried to shrink to a larger capacity");
 

src/libstd/collections/hash/set.rs

@@ -315,7 +315,7 @@ impl<T, S> HashSet<T, S>
     /// assert!(set.capacity() >= 2);
     /// ```
     #[inline]
-    #[unstable(feature = "shrink_to", reason = "new API", issue="0")]
+    #[unstable(feature = "shrink_to", reason = "new API", issue="56431")]
     pub fn shrink_to(&mut self, min_capacity: usize) {
         self.map.shrink_to(min_capacity)
     }

src/libstd/ffi/os_str.rs

@@ -324,7 +324,7 @@ impl OsString {
     /// assert!(s.capacity() >= 3);
     /// ```
     #[inline]
-    #[unstable(feature = "shrink_to", reason = "new API", issue="0")]
+    #[unstable(feature = "shrink_to", reason = "new API", issue="56431")]
     pub fn shrink_to(&mut self, min_capacity: usize) {
         self.inner.shrink_to(min_capacity)
     }