1371996 - Mark extensions as negotiated consistently

Status: NEW

(NSS :: Libraries, enhancement, P3)

Description

[Martin Thomson [:mt:]]

There are plenty of places where we mark extensions as negotiated, but we do so in a brittle way.  We should fix this, either by

1. adding an outparam to extension handlers so that the value can be set consistently, or

2. creating booleans in xtnData for each extension that actually cares about this.  We already have this in some cases, like extended master secret, I think.  A boolean would be more efficient to look up.