Add implementation for SRTP_KERNEL_LINUX.
Add implementation for SRTP_KERNEL_LINUX.

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