Bug#741136: brltty: Very unstable in Debian Installer 7.4

[Samuel Thibault <sthibault@debian.org>]

Hello Dave,

We have a bug report in Debian where brltty crashes during
clock configuration, see http://bugs.debian.org/741136

I believe what happens is that brltty is disturbed by the sudden
clock change.  Indeed, I can see uses of getCurrentTime()
where getMonotonicTime() should probably be used instead, in
asyncRelativeAlarm(), asyncWait().

Also, the bug report is about a HandyTech device, and I see some
synchronization code in synchronizeDateTime(), perhaps this has to be
checked too?  But I'm also seeing a brltty hang with the Baum driver, so
the fix above would be needed anyway?

Lastly, CLOCK_MONOTONIC_RAW should probably be used when available, as
it provides a clock with no drift at all (even not adjtimex).

Samuel