terminal state for kernel console output.
r56043 in 2000 added many complications to support dynamic selection
of the terminal emulator using modules and the ioctl CONS_SETTERM.
This was never completed. There are still no modules, but it is easy
to restore the scterm and dumb emulators at compile time. Then
boot-time configuration for the preferred one doesn't work right, but
CONS_SETTERM almost works after fixing this bug. CONS_SETTERM only
switches the emulator for the user state, leaving the kernel state(s)
still using the boot-time emulator. The fix is especially important
when switching from sc to scteken, since the scteken state has pointers
in it.
Rename kernel_console_ts to sc_kts.
7db291d201