Seems to fix or reduce deadlocks

Instead of two!!

Removal of libs/libiax2 from the git repo.
Use instead sflphone-iax2-dev from the sflphone repo.
Other debian package available: sflphone-iax2

To execute the program you only need sflphone-iax2; to compile it, you need the headers in sflphone-iax2-dev

Website update + clean build system

SFLPhone will now compile and run without libiax, but I can't carantee it won't crash.

The previous commit brought a segmentation fault when launching the client.
When the daemon is lauched separatly, it uses a wrapper script, but it doesn't when the client start the daemon.
SO the LD_LIBRARY_PATH was ignored and the daemon couldn't find the dynamic library for the codecs.

Codecs dynamic libraries are created at the compilation time if they don't exist and copied in /usr/lib/sflphone/codecs at the installation