PR/48475: YAMAGUCHI Takanori: EDNS option broken with unbound. struct
querybuf in net/gethnamaddr.c defines MAXPACKET to 64K. This in turn
gets passed down until it reached res_nopt(..., answer, anslen), where
the size of the buffer must fit in 16 bits. Unfortunately we end up
being one more than the max so we end up sending a 0 as the size and
unbound does not like that. Instead we clip now to 64K - 1, and everyone
is happy.
XXX: Pullup to 7.