Feature Request: Allow collapsing multi-line annotations to a single line for display.

[GoogleCodeExporter]

When creating a multi-line annotation, there's no way to hide or collapse it, 
to get it out of the way, when I'm interested in seeing only the underlying 
source material.

* What steps will reproduce the problem?

1. Create a new annotation that's several lines long (use C-j or C-m to add new 
lines).
2. Verify that the annotation spans multiple lines.
3. Verify that the annotation cannot be collapsed to a single line, or hidden.

* What version of the product are you using? On what operating system?

Revision 45, Cygwin.

Original issue reported on code.google.com by [email protected] on 17 Aug 2012 at 3:48