[9fans] tbl fail

[erik quanstrom]

tbl's calculation for how many columns it can handle is
wrong.  sizeof(nregs) = nelem(nregs)*sizeof(char*).
it appears that tbl is assuming *2-byte pointers*!

huzzah!

- erik

/n/dump/2013/0104/sys/src/cmd/tbl/tr.c:20,26 - tr.c:20,26
  char  *
  reg(int col, int place)
  {
-       if (sizeof(nregs) < 2 * 3 * qcol)
+       if(qcol*place+col >= nelem(nregs)-1)
                error("Too many columns for registers");
        return (nregs[qcol*place+col]);
  }