starter48

Results 4 issues of starter48

Can you please add a free G729 codec into the codec pack? [It is royalty free since 2017 year](http://www.sipro.com/G729.html).

Please add Symmetric RTP option. It can help to traverse some NATs better.

Can you make it available for modern Thunderbird also?

**load16_be()** function is inefficient and basically does the same work as **ntohs()**.