Fix string handling to avoid problems in Android

Use a temporay std::string variable to hold an intermediate result, use this
to get the real C char string. As an additional safty feature use a counted
string comapre.
Fix building of small demo test application
Add some checks and make code more defensive
Provide some more crypto info even if not yet secure
Remove verbose logging
Update inline documentation
Remove (comment) old GoClear code, not implemented
Enhance log and error counters and handling of messages

ZRTP and SDES have own counters for protect and unprotect RTP/SRTP data and moved
these counters to the public area of the class.

Prepend each the info/warning/error string with a unique identification that
mirrors the sevrity and message code in ZrtpCodes.h. Applications may use this
id code to identify messages in an easy way. The id code conforms to Android's
XML naming restrictions.

replace the fixed ZRTP sequence number start with randomized data.
Fix threshold counting
Add global logging functions pointer, fix statistic counter
Fix small typo in comment
Fix and enhance inline documentation
Fix initialization of conf2Ack simulation event
Fix ZRTP sequence number initialization
Implement ZRTP protocol version negotiation

This version implements protocol negotiation according to RFC6189, section
4.1.1. This new function required modifications on the external interface to
provide additional information from and to applications. See documentation.

Currently the library supports only version 1.1 and is compatible with
previous versions on protocol level.

Applications shall use the new library even if the don't use the new or
modified interface functions. This will guarantee that the application are
prepared once a new ZRTP protocol version is available. Application shall use
the new/modified interfaces if they require and handle ZRTP hello hashes.
Remove the debug output and move comment lines
Small fix in public key algorithm selection

Build own intersecting list correctly, change names of lists and variable to
make it more readable.
Fix handling of supported protocol versions

Add a new define that defines the number of currently supported
version. This avoids out-of-bounds access of array.
Merge branch 'master' of https://github.com/wernerd/ZRTPCPP