Tweak buffer sizes to prevent compilation warnings

Tweak buffer sizes to prevent compilation warnings

For some libc implementations, BUFSIZ is small enough (e.g. 1024 for
musl libc) to trigger compilation warnings about insufficient size of
certain buffers.  Since the relevant buffers are used for printing DNS
names, increase their size to '(n + 1) * DNS_NAME_FORMATSIZE', where 'n'
is the number of DNS names which are printed to a given buffer.  This
results in somewhat arbitrary, albeit nicely-aligned and large enough
buffer sizes.