Restructuring of directories for SRTP and ZRTP files

All,

to have a more clean include directory structure after installation
of GNU ccRTP I moved the directories that contain SRTP and ZRTP files
into the src/ccrtp directory instead of having them in parallel to the
ccrtp directory. When you do an update please make sure you use the
-d -P options to get the new directories and to prune the old ones.

Regards,
Werner