Add doc aliases for "delete"

This patch adds doc aliases for "delete". The added aliases are
supposed to reference usages `delete` in other programming
languages.

- `HashMap::remove`, `BTreeMap::remove` -> `Map#delete` and `delete`
  keyword in JavaScript.

- `HashSet::remove`, `BTreeSet::remove` -> `Set#delete` in JavaScript.

- `mem::drop` -> `delete` keyword in C++.

- `fs::remove_file`, `fs::remove_dir`, `fs::remove_dir_all`
  -> `File#delete` in Java, `File#delete` and `Dir#delete` in Ruby.

Before this change, searching for "delete" in documentation
returned no results.

library/alloc/src/collections/btree/map.rs

@@ -823,6 +823,7 @@ impl<K: Ord, V> BTreeMap<K, V> {
     /// assert_eq!(map.remove(&1), Some("a"));
     /// assert_eq!(map.remove(&1), None);
     /// ```
+    #[doc(alias = "delete")]
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn remove<Q: ?Sized>(&mut self, key: &Q) -> Option<V>
     where

library/alloc/src/collections/btree/set.rs

@@ -770,6 +770,7 @@ impl<T: Ord> BTreeSet<T> {
     /// assert_eq!(set.remove(&2), true);
     /// assert_eq!(set.remove(&2), false);
     /// ```
+    #[doc(alias = "delete")]
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn remove<Q: ?Sized>(&mut self, value: &Q) -> bool
     where

library/core/src/mem/mod.rs

@@ -889,6 +889,7 @@ pub fn replace<T>(dest: &mut T, mut src: T) -> T {
 /// ```
 ///
 /// [`RefCell`]: crate::cell::RefCell
+#[doc(alias = "delete")]
 #[inline]
 #[stable(feature = "rust1", since = "1.0.0")]
 pub fn drop<T>(_x: T) {}

library/std/src/collections/hash/map.rs

@@ -859,6 +859,7 @@ where
     /// assert_eq!(map.remove(&1), Some("a"));
     /// assert_eq!(map.remove(&1), None);
     /// ```
+    #[doc(alias = "delete")]
     #[inline]
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn remove<Q: ?Sized>(&mut self, k: &Q) -> Option<V>

library/std/src/collections/hash/set.rs

@@ -874,6 +874,7 @@ where
     /// assert_eq!(set.remove(&2), true);
     /// assert_eq!(set.remove(&2), false);
     /// ```
+    #[doc(alias = "delete")]
     #[inline]
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn remove<Q: ?Sized>(&mut self, value: &Q) -> bool

library/std/src/fs.rs

@@ -1524,6 +1524,7 @@ impl AsInner<fs_imp::DirEntry> for DirEntry {
 ///     Ok(())
 /// }
 /// ```
+#[doc(alias = "delete")]
 #[stable(feature = "rust1", since = "1.0.0")]
 pub fn remove_file<P: AsRef<Path>>(path: P) -> io::Result<()> {
     fs_imp::unlink(path.as_ref())
@@ -1958,6 +1959,7 @@ pub fn create_dir_all<P: AsRef<Path>>(path: P) -> io::Result<()> {
 ///     Ok(())
 /// }
 /// ```
+#[doc(alias = "delete")]
 #[stable(feature = "rust1", since = "1.0.0")]
 pub fn remove_dir<P: AsRef<Path>>(path: P) -> io::Result<()> {
     fs_imp::rmdir(path.as_ref())
@@ -1995,6 +1997,7 @@ pub fn remove_dir<P: AsRef<Path>>(path: P) -> io::Result<()> {
 ///     Ok(())
 /// }
 /// ```
+#[doc(alias = "delete")]
 #[stable(feature = "rust1", since = "1.0.0")]
 pub fn remove_dir_all<P: AsRef<Path>>(path: P) -> io::Result<()> {
     fs_imp::remove_dir_all(path.as_ref())