rollup merge of #19710: steveklabnik/gh15449

Fixes #15499.

src/libstd/io/buffered.rs

@@ -80,7 +80,7 @@ impl<R: Reader> BufferedReader<R> {
 
     /// Gets a mutable reference to the underlying reader.
     ///
-    /// ## Warning
+    /// # Warning
     ///
     /// It is inadvisable to directly read from the underlying reader.
     pub fn get_mut(&mut self) -> &mut R { &mut self.inner }
@@ -185,7 +185,7 @@ impl<W: Writer> BufferedWriter<W> {
 
     /// Gets a mutable reference to the underlying write.
     ///
-    /// ## Warning
+    /// # Warning
     ///
     /// It is inadvisable to directly read from the underlying writer.
     pub fn get_mut(&mut self) -> &mut W { self.inner.as_mut().unwrap() }
@@ -357,7 +357,7 @@ impl<S: Stream> BufferedStream<S> {
 
     /// Gets a mutable reference to the underlying stream.
     ///
-    /// ## Warning
+    /// # Warning
     ///
     /// It is inadvisable to read directly from or write directly to the
     /// underlying stream.

src/libstd/io/stdio.rs

@@ -127,7 +127,7 @@ impl StdinReader {
     ///
     /// This provides access to methods like `chars` and `lines`.
     ///
-    /// ## Example
+    /// # Examples
     ///
     /// ```rust
     /// use std::io;