Strap Buckle Clip

This is the female part for http://www.thingiverse.com/thing:1416

Version 1:

I cleaned up some errors in the STL of the original
using NetFabb-Basic (Linux).
http://www.netfabb.com/news.php?nid=10

Improved version 2:

* The large bridge got some pads the filament can "land on" because the first few strands just fall down and make a mess inside the object with version 1.
* The smaller bridges got even shorter by rounding the walls inwards
* the clip is a few mm shorter, allowing t