MFC r238935,238960:

MFC r238935,238960:

  Properly apply #ifdef INET and leave a comment that we are (will) apply
  delayed IPv6 checksum processing in ip6_output.c when doing IPsec.

  In case of IPsec he have to do delayed checksum calculations before
  adding any extension header, or rather before calling into IPsec
  processing as we may send the packet and not return to IPv6 output
  processing here.

PR:		kern/170116
Approved by:	re (kib)

git-svn-id: svn://svn.freebsd.org/base/releng/9.1@240194 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f