unix-pc fix for arc 5.21

[Robert E. Stampfli]

For those of you that are trying to get the version of arc 5.21, recently
posted by Howard Chu, to run on your unix-pc, I encountered what I believe
is a compiler bug.  I am running a 7300 with Unix 3.5.1.3.  The bug
manifests itself in that a function declared as an unsigned char will,
if given the opportunity, return a negative number.  I got arc to run by
doing the following:

In the file arccode.c I changed the defn of the argument to the function code()
from
	char c;			/* character to encode */
to
	unsigned char c:	/* character to encode */

That's all.  Needless to say, this was a bear to find.  I have not tried
compiling the original arc with gnu-cc, but have on several other flavors of
machines with no replication of this bug.

I also fixed several other bugs in the process of hunting this one down,
but they were either benign or legitimate coding errors that have already
been reported to the applicable newsgroups.

att!cbnews!res
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Rob Stampfli