view: thread using <ul> instead of <table>

view: thread using <ul> instead of <table>

On second viewing, this does render small cues which makes the
output more pleasant for lynx users.  We avoid injecting the
root (level=0) message into a list since it still wastes
precious horizontal whitespace on small displays.

This also results in small reductions in bandwidth usage as
it takes fewer tags/whitespace to render unordered lists.