bgpd: fix build on Solaris

bgpd: fix build on Solaris

* Solaris doesn't have u_int64_t, so use uint64_t instead. C99-style
  fixed-width integers should always be preferred to improve portability;

* 's_addr' is a macro on Solaris, so we can't use it as a variable name.
  Rename the 's_addr' variable to 'addr' in the
  bgp_peer_conf_if_to_su_update_v4() function.

Signed-off-by: Renato Westphal <renato@opensourcerouting.org>