8527 tty buffer/queue sizes should be larger

@@ -378,11 +378,11 @@
         sop = (struct stroptions *)mop->b_rptr;
         if (oflag & FNOCTTY)
                 sop->so_flags = SO_HIWAT | SO_LOWAT;
         else
                 sop->so_flags = SO_HIWAT | SO_LOWAT | SO_ISTTY;
-        sop->so_hiwat = 512;
+        sop->so_hiwat = _TTY_BUFSIZ;
         sop->so_lowat = 256;
         putnext(rqp, mop);
 
         /*
          * The input, devp, is a major device number, the output is put