[krbdev.mit.edu #7143] krb5_set_trace_filename not exported

[Russ Allbery <rra@stanford.edu> via RT]

I finally implemented an option to pam-krb5 to enable trace logging for
debugging (pam-krb5 almost always uses a secure context, so the
environment variable doesn't work), only to find that while
krb5_set_trace_filename is prototyped in krb5.h, it isn't exported by
the library.  I assume this is an oversight?