Avoid legacy CSS2 syntax for the "display" property and use the CSS3

Avoid legacy CSS2 syntax for the "display" property and use the CSS3
two-value syntax "display: inline flow;" instead.  In particular, there
is no need to establish a new block formatting context with "flow-root",
and in fact that's detrimental because it appears to introduce spurious
soft-wrap opportunities.

jmc@ reported a bogus line break between the opening angle bracket
generated by .Aq Mt and the following email address.