Fix spelling errors and capitalization.

src/librustdoc/html/render.rs

@@ -1155,7 +1155,7 @@ impl Context {
 
             // We have a huge number of calls to write, so try to alleviate some
             // of the pain by using a buffered writer instead of invoking the
-            // write sycall all the time.
+            // write syscall all the time.
             let mut writer = BufferedWriter::new(w);
             if !cx.render_redirect_pages {
                 try!(layout::render(&mut writer, &cx.layout, &page,

src/librustdoc/stability_summary.rs

@@ -11,7 +11,7 @@
 //! This module crawls a `clean::Crate` and produces a summarization of the
 //! stability levels within the crate. The summary contains the module
 //! hierarchy, with item counts for every stability level per module. A parent
-//! module's count includes its childrens's.
+//! module's count includes its children's.
 
 use std::ops::Add;
 use std::num::Zero;