Bug fix for COPY-READTABLE

[Taiichi Yuasa <yuasa%tutics.tut.junet%utokyo-relay.csnet@RELAY.CS.NET>]

A bug was detected by Dieter Boecker in Germany.
I cannot send this bug fix to him, because he used an illegal
route to send his bug report.  (I'm sure he didn't know the route is
illegal.)  If you know how to reach him legally,
please forward this message.  His UUCP address is unido!ifistg!dieter.
Thank you.

The bug was about COPY-READTABLE.  If you supply a readtable as the second
argument to COPY-READTABLE, then the KCL process will die.  To fix the bug,
add the following two lines (marked =>) to the definition of the C function
copy_readtable in file c/read.d.

	if (to == Cnil) {
		....
=>	} else
=>		rtab = to->rt.rt_self;
	for (i = 0;  i < RTABSIZE;  i++)
		....

-- Taiichi