krb4 library major version bump

[Ken Raeburn]

With various strncpy->strcpy changes fixed up, Sam was still running
into the problem, so I've been looking further.

Currently, aklog is crashing for me while printing an error message.
It's getting the error message by indexing into krb_err_txt.  In
previous releases, this was a char*[256] array.  Now it's a char**.
That's another incompatible change.  Tom checked it in in December as
part of merging some of the Mac code.  Is this change required?

Even if it weren't for this problem, aklog was still trying to report
a "can't send request to KDC" type error when it shouldn't have.  So
there's at least one more incompatible change from the previous krb4
ABI, or there's just some bug where it doesn't work at all and our
testing hasn't caught it.

Ken