[orca-list] More flat review rewrite goodness: giant-table issues fixed

[Joanmarie Diggs <jdiggs igalia com>]

Hey all.

You should know the refrain by now ("I've still got a long way to go,
but....") <smiles>

I've just merged in some changes which should make invoking flat review
in tables much more efficient. Especially in giant tables. My test case
was a Thunderbird folder with over 40,000 messages. Before Orca would
not respond for a really long time; now it responds in 2 seconds. And
I've got other not-yet-merged changes that will make it faster than
that. But I hope you'll agree that going from an uber-long time to 2
seconds was worth committing in the meantime.

To finish the familiar tune on a familiar note: Please pull master, let
me know what you think, and especially if I've broken something.

Thanks!
--joanie