Rollup merge of rust-lang#36851 - tmiasko:fix-read-until-docs, r=bluss

Fix BufRead::read_until documentation.

Second paragraph already fully explains what happens when EOF is
encountered. The third paragraph (removed one) is spurious and
misleading.

Author: steveklabnik

src/libstd/io/mod.rs

@@ -1264,15 +1264,13 @@ pub trait BufRead: Read {
     #[stable(feature = "rust1", since = "1.0.0")]
     fn consume(&mut self, amt: usize);
 
-    /// Read all bytes into `buf` until the delimiter `byte` is reached.
+    /// Read all bytes into `buf` until the delimiter `byte` or EOF is reached.
     ///
     /// This function will read bytes from the underlying stream until the
     /// delimiter or EOF is found. Once found, all bytes up to, and including,
     /// the delimiter (if found) will be appended to `buf`.
     ///
-    /// If this reader is currently at EOF then this function will not modify
-    /// `buf` and will return `Ok(n)` where `n` is the number of bytes which
-    /// were read.
+    /// If successful, this function will return the total number of bytes read.
     ///
     /// # Errors
     ///
@@ -1315,9 +1313,7 @@ pub trait BufRead: Read {
     /// up to, and including, the delimiter (if found) will be appended to
     /// `buf`.
     ///
-    /// If this reader is currently at EOF then this function will not modify
-    /// `buf` and will return `Ok(n)` where `n` is the number of bytes which
-    /// were read.
+    /// If successful, this function will return the total number of bytes read.
     ///
     /// # Errors
     ///