Add clippy.swf to support copying download commands to the clipboard

This just makes it that much easier to quickly download one patch
from an existing change.  Thanks to GitHub for their MIT licensed
SWF that makes this easily possible.

Unfortunately we have to build the HTML up as a string and install
it with innerHTML in order to work around a bug in ie6.  Any other
browser allowed us to build this up using standard DOM objects, but
in ie6 the SWF "movie" doesn't load unless we create the <object>
tag through assignment to innerHTML on a container <div>.

Signed-off-by: Shawn O. Pearce <sop@google.com>