Raise the default value of TTYHOG from 1 kB to 8 kB. Since TTYHOG is

Raise the default value of TTYHOG from 1 kB to 8 kB.  Since TTYHOG is
an administrative limit on the size of tty/pty input buffers, this is
mostly an inconsequential change.  (slti(4) will allocate an 8 kB
static buffer instead of a 1 kB buffer due to a hack in the driver.)
The increase happens to kludge around a lame limitation of syscons,
which does not allow one to paste more than TTYHOG bytes.

PR:		42031
Reviewed by:	mike (mentor)