Rollup merge of rust-lang#140952 - SimonSapin:ascii_whitespace_definition, r=dtolnay

Specify that split_ascii_whitespace uses the same definition as is_ascii_whitespace

Author: jhpratt

library/core/src/str/mod.rs

@@ -1173,6 +1173,7 @@ impl str {
     /// The iterator returned will return string slices that are sub-slices of
     /// the original string slice, separated by any amount of ASCII whitespace.
     ///
+    /// This uses the same definition as [`char::is_ascii_whitespace`].
     /// To split by Unicode `Whitespace` instead, use [`split_whitespace`].
     ///
     /// [`split_whitespace`]: str::split_whitespace
@@ -1191,7 +1192,8 @@ impl str {
     /// assert_eq!(None, iter.next());
     /// ```
     ///
-    /// All kinds of ASCII whitespace are considered:
+    /// Various kinds of ASCII whitespace are considered
+    /// (see [`char::is_ascii_whitespace`]):
     ///
     /// ```
     /// let mut iter = " Mary   had\ta little  \n\t lamb".split_ascii_whitespace();