fix($location): consider baseHref in relative link for legacy browsers

Request Type: bug
 
**How to reproduce:**

In a legacy browser that doesn't support HTML5 push state (ie: IE9) have the following:

- `$locationProvider.html5Mode(true).hashPrefix('!');` in app configuration;
- a number of routes such as `/foo`, `/bar` in the `$routeProvider` configuration;
- `<base href="/en/">` in page headers;
- `<a href="/en/foo">` in a link.

When clicking a link, it is rewritten as: `http://host/en/#!/en/foo` 
Expected: `http://host/en/#!/foo`

Component(s): $location

Impact: medium

Complexity: small

This issue is related to: 



**Other Comments:**

I couldn't yet devise any test for covering this case. This fix concern a click handler on the `$rootElement` which (afaik) is not covered in the current tests.

Please let me know if you find it reasonable and if you have ideas on how to test for it.
Thanks!