Support for popup-follows-cursor and bugfixes

- Fix performance problems on massive pages with tons of elements (e.g. long 4chan threads)
- Fix the fallback for not looking up within the lookup on android and make it apply to sticky mode too
- Fix for a general performance issue with backwards lookups
- Fix for how context separation works
- Fix for ignoring hard newlines
- Workaround for absolute-positioned span elements to allow some display:block elements to get jumped outside of by the text grabbing code

options.js

@@ -59,6 +59,12 @@ function defaults()
         default: true,
         label: "Strict matching for alternative matches"
     });
+    settings.push({
+        id: "popup_follows_mouse",
+        kind: "checkbox",
+        default: true,
+        label: "Popup follows mouse (even if it doesn't update)"
+    });
     
     // display
     settings.push({