Rationalize CMSG_SPACE usage:

Rationalize CMSG_SPACE usage:

  in lib/zebra.h, ensure that RFC3542-required CMSG_SPACE and CMSG_LEN
  are defined.  Warn if alignment assumptions are made, since they are
  i386-centric.

  in lib/sockopt.h, declare that sockopt sizes are without
  CMSG_SPACE-required padding - just simple sizeof.

  in ospfd/ospf_packet.c, simply use CMSG_SPACE

This should remove all instances of CMSG_ALIGN from the source code.
This is a nonstandard, though rational, construct; quagga should use
only those defines in RFC3542.