Make it possible to include srtp.h from C++ code.
Make it possible to include srtp.h from C++ code.

cuijinquan/libsrtp,persmule/libsrtp,yarrcc/libsrtp-ios,ksophocleous/libsrtp,ksophocleous/libsrtp,cuijinquan/libsrtp,persmule/libsrtp,cuijinquan/libsrtp,yarrcc/libsrtp-ios,Distrotech/libsrtp,persmule/libsrtp,yarrcc/libsrtp-ios,Distrotech/libsrtp