Sidebar clipboard content tooltip should render Unicode/HTML escapes safely (with no active links, etc.)

[greenfeld]

1. Highlight a line of text in Read in a EPUB or PDF file which has non-base-ASCII characters (Unicode accented or non-European), quotes, long/em-dashes, or similar in it.
2. Copy it to the clipboard using the Copy button in Read.
3. Use the mouse to hover over the clipboard contents item for the item just pasted. The tooltip will show the raw unicode/HTML escapes/etc., although pasting to applications (from the Sugar clipboard) will negotiate how these get interpreted to ensure something usable shows.

(Note that the tooltip will only show the first line if you copy more than one to the clipboard.)

Seen with OLPC 12.1.0 os21.