[krbdev.mit.edu #1158] substitutions needed on man pages

[Ken Raeburn via RT]

Both krb5.conf and kdc.conf need substitutions done to use the correct
pathnames.

Also, krb5.conf should list all the files in the search path
(/etc/krb5.conf and $prefix/etc/krb5.conf in the normal unix build,
different on Mac I think), and if it doesn't already, describe the
interactions between multiple files.

I don't know if pathnames are put into other man pages in the tree...