Add suckerfish menu for IE6

The code for Multiflex-3 is now cloning from suckerfish with some modification. Most logic are identical. You may compare the code for more idea.

The main different is: Multiflex-3 implementation is a purely CSS-based version. For sure that because I am not a big fans with JavaScript, but this also come with other consideration:

1. This theme is target for Acid2 compatible browsers, e.g. FF2/3, Opera9.2/9.5, Safari3, and even IE7 (partly compatible). I give a hook (fix-ie.css and fix-ie-rtl.css) for IE6 fix contribution, but I am not going to support IE6 officially.
2. Many implementation may break in IE6, but not only the menu. E.g. PNG, fluid width layout and so on. Trim down the fancy IE6 supported menu implementation as CSS-based will greatly simplify the maintenance difficulties.
3. I hope to promote the "kick away of IE6". If theme looks basically function with IE6, thanks god; If using IE6 will give you some functionality cut off, please don't use IE6 ;p

Long story short: If the changes can benefit for IE6 plus: 1. only PHP, HTML and CSS based, 2. not table based (original Multiflex-3 implementation) with conditional branch, and 3. not JavaScript based, please feel free to contribute and I will integrate them into next release.

Please understand that I am the only maintainer of this theme (at least right now) and so also need to consider the resource and effort required for maintain this theme in a high quality :S

I have just created a csshover module which may or may not work with the menu implementation in this module.

While I agree with getting rid of IE6 as fast as possible, I do think some people won't be able to, such as those that are using locked down systems at work, so an alternative approach can sometimes be wanted.