Fixed IE-related issues in CSS

In IE there are a few issues in magicsuggest layout that should be fixed:
* IE's internal 'clear button' pseudo-element (http://msdn.microsoft.com/en-us/library/windows/apps/hh465740.aspx) is sometimes overlapping the dropdown button.
![ms_-ms-clear](https://cloud.githubusercontent.com/assets/4599428/3083809/43d7dd76-e4e9-11e3-9fda-52ad1b01a613.jpg)

* 'ms-close-btn' position is broken when using 'ms-stacked' for results layout.
![ms_ms-close-btn](https://cloud.githubusercontent.com/assets/4599428/3083812/497f001a-e4e9-11e3-94cd-f4e33c899540.jpg)

Both problems should be fixed with these proposed changes to CSS:
![ms_fixed](https://cloud.githubusercontent.com/assets/4599428/3083816/54f45544-e4e9-11e3-9aca-1905080acfa1.JPG)

Hope we can merge it to trunk.