PBKDF2-HMAC-SHA256 Patch for splitted kernel.

Line below produces segfault, this does not occurs with -O0 in CFLAGS.
//HANDLE_CLERROR(clReleaseMemObject(mem_state), "Release mem state");

Since this is called only on exit, I commented it and it should be no
big problems with that.

Performance is ~1% worse, but I see no X lags anymore.
pbkdf2-hmac-sha256-opencl: Immediate response to keystroke.