Fix doc example, and change fn annotation to stable

Author: 1011X

src/libcore/ascii.rs

@@ -31,7 +31,7 @@ use iter::FusedIterator;
 /// documentation for more.
 ///
 /// [`escape_default`]: fn.escape_default.html
-#[unstable(feature = "core_ascii", issue = "46409")]
+#[stable(feature = "core_ascii", since = "1.26.0")]
 pub struct EscapeDefault {
     range: Range<usize>,
     data: [u8; 4],
@@ -57,8 +57,7 @@ pub struct EscapeDefault {
 /// # Examples
 ///
 /// ```
-/// #![no_std]
-/// use core::ascii;
+/// use std::ascii;
 ///
 /// let escaped = ascii::escape_default(b'0').next().unwrap();
 /// assert_eq!(b'0', escaped);
@@ -100,7 +99,7 @@ pub struct EscapeDefault {
 /// assert_eq!(b'9', escaped.next().unwrap());
 /// assert_eq!(b'd', escaped.next().unwrap());
 /// ```
-#[unstable(feature = "core_ascii", issue = "46409")]
+#[stable(feature = "core_ascii", since = "1.26.0")]
 pub fn escape_default(c: u8) -> EscapeDefault {
     let (data, len) = match c {
         b'\t' => ([b'\\', b't', 0, 0], 2),