Extracted shorthands to separate files.

I've deliberately tried to keep things similarly structured as in the longhand files. I.e. if a given property is in e.g. longhand/box.mako.rs, the shorthand stuff that relates to the same property is in shorthand/box.mako.rs and so forth.

components/style/properties/shorthand/inherited_text.mako.rs

@@ -0,0 +1,14 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+<%namespace name="helpers" file="/helpers.mako.rs" />
+
+// Per CSS-TEXT 6.2, "for legacy reasons, UAs must treat `word-wrap` as an alternate name for
+// the `overflow-wrap` property, as if it were a shorthand of `overflow-wrap`."
+<%helpers:shorthand name="word-wrap" sub_properties="overflow-wrap">
+    use properties::longhands::overflow_wrap;
+    Ok(Longhands {
+        overflow_wrap: Some(try!(overflow_wrap::parse(context, input))),
+    })
+</%helpers:shorthand>