Fix a few typos in the code

Author: sylvestre

src/librustdoc/html/highlight.rs

@@ -107,7 +107,7 @@ pub enum Class {
 ///
 /// The classifier will call into the `Writer` implementation as it finds spans
 /// of text to highlight. Exactly how that text should be highlighted is up to
-/// the implemention.
+/// the implementation.
 pub trait Writer {
     /// Called when we start processing a span of text that should be highlighted.
     /// The `Class` argument specifies how it should be highlighted.

src/librustdoc/html/render.rs

@@ -2721,7 +2721,7 @@ impl<'a> fmt::Display for Sidebar<'a> {
         let parentlen = cx.current.len() - if it.is_mod() {1} else {0};
 
         // the sidebar is designed to display sibling functions, modules and
-        // other miscellaneous informations. since there are lots of sibling
+        // other miscellaneous information. since there are lots of sibling
         // items (and that causes quadratic growth in large modules),
         // we refactor common parts into a shared JavaScript file per module.
         // still, we don't move everything into JS because we want to preserve

src/libstd/memchr.rs

@@ -239,7 +239,7 @@ mod fallback {
         text[..offset].iter().rposition(|elt| *elt == x)
     }
 
-    // test fallback implementations on all plattforms
+    // test fallback implementations on all platforms
     #[test]
     fn matches_one() {
         assert_eq!(Some(0), memchr(b'a', b"a"));