Clean-up, fixes, and enhancements to ZRTP

[Werner Dittmann]

All,

checked in a better version of the ZRTP code. It contains fixes
to support Zfone Beta 2 (it is nearly "bug-compatible" :-)  ).

Also some enhancements with respect to the GoClear facility of
ZRTP - not yet complete, but some code is already there.

Cleanup of code.

The same ZRTP implementation (the protocol engine) is now available
as part of the GNU ccRTP stack (not yet released, use CVS HEAD) and
is of course inter operable with minisip. Together with Michel de Boers
we tested this with the combination of GNU ccRTP and twinkle. Any client
that uses GNU ccRTP now can use ZRTP with just a few lines of code
change (about 10 lines of code change in twinkle to support basic ZRTP,
implementing the user interface in twinkle's GUI needed some more changes
of course).

Regards,
Werner