Cross-reference fs::read functions from io::Read docs

Author: mbrubeck

src/libstd/io/mod.rs

@@ -595,6 +595,9 @@ pub trait Read {
     ///     Ok(())
     /// }
     /// ```
+    ///
+    /// (See also the [`std::fs::read`] convenience function for reading from a
+    /// file.)
     #[stable(feature = "rust1", since = "1.0.0")]
     fn read_to_end(&mut self, buf: &mut Vec<u8>) -> Result<usize> {
         read_to_end(self, buf)
@@ -633,6 +636,9 @@ pub trait Read {
     ///     Ok(())
     /// }
     /// ```
+    ///
+    /// (See also the [`std::fs::read_to_string`] convenience function for
+    /// reading from a file.)
     #[stable(feature = "rust1", since = "1.0.0")]
     fn read_to_string(&mut self, buf: &mut String) -> Result<usize> {
         // Note that we do *not* call `.read_to_end()` here. We are passing