jquery.suggestions: Handle CSS ellipsis better for IE

IE is not impressed by our puny hacks and still reports the width
"in context of" the position in the document, limited by the width
of ancestor elements.

Let's temporarily apply position: absolute; to the involved elements.
This pulls them out of normal document flow and lets us figure out the
real width at last.

Also wrote a proper comment on why we need this stuff.

Verified that this fixes:
* IE 8
* IE 11

Verified that it doesn't break:
* Firefox 3.6
* Firefox 29
* Opera 12
* Opera 22

It *does not* fix IE 6. I don't think that investigating why is a good
use of my time, so I didn't. I84fbae5a made the functionality usable
on IE 6, which feels good enough for me.

Bug: 65224
Change-Id: I4a7357543ca244585ade2061b92f5a6d1e439278
(cherry picked from commit 1a04fb81cfca8bde9b05ceb17aa7775d94fcf24c)