Enable secure TTY input buffer flushing by default.
Enable secure TTY input buffer flushing by default.

I'm leaving the sysctl there. If people really notice a slowdown, they
can revert to the old behaviour.

Discussed with:	kib

jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase