Fix commonmark Markdown warnings in docs, part 1

Fixes warnings from rust-lang/rust#44229 when `--enable-commonmark` is
passed to rustdoc.

This is mostly a global find-and-replace for bare URIs on lines by
themselves in doc comments.

components/style/servo/media_queries.rs

@@ -94,7 +94,7 @@ impl Device {
 
     /// Sets the body text color for the "inherit color from body" quirk.
     ///
-    /// https://quirks.spec.whatwg.org/#the-tables-inherit-color-from-body-quirk
+    /// <https://quirks.spec.whatwg.org/#the-tables-inherit-color-from-body-quirk>
     pub fn set_body_text_color(&self, _color: RGBA) {
         // Servo doesn't implement this quirk (yet)
     }
@@ -155,13 +155,13 @@ impl Device {
 #[derive(Clone, Debug, PartialEq)]
 #[cfg_attr(feature = "servo", derive(HeapSizeOf))]
 pub enum ExpressionKind {
-    /// http://dev.w3.org/csswg/mediaqueries-3/#width
+    /// <http://dev.w3.org/csswg/mediaqueries-3/#width>
     Width(Range<specified::Length>),
 }
 
 /// A single expression a per:
 ///
-/// http://dev.w3.org/csswg/mediaqueries-3/#media1
+/// <http://dev.w3.org/csswg/mediaqueries-3/#media1>
 #[derive(Clone, Debug, PartialEq)]
 #[cfg_attr(feature = "servo", derive(HeapSizeOf))]
 pub struct Expression(pub ExpressionKind);

components/style/servo/url.rs

@@ -21,7 +21,7 @@ use values::computed::{Context, ToComputedValue, ComputedUrl};
 /// eagerly resolving with rust-url would be duplicated work.
 ///
 /// However, this approach is still not necessarily optimal: See
-/// https://bugzilla.mozilla.org/show_bug.cgi?id=1347435#c6
+/// <https://bugzilla.mozilla.org/show_bug.cgi?id=1347435#c6>
 #[derive(Clone, Debug, Deserialize, HeapSizeOf, Serialize)]
 pub struct SpecifiedUrl {
     /// The original URI. This might be optional since we may insert computed