Merge r253680,253805 from head:

Merge r253680,253805 from head:
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  r253680 | des | 2013-07-26 19:53:43 +0400 (Fri, 26 Jul 2013) | 7 lines

  Implement certificate verification, and many other SSL-related
  imrovements; complete details in the PR.

  PR:             kern/175514
  Submitted by:   Michael Gmelin <freebsd@grem.de>
  MFC after:      1 week

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  r253805 | des | 2013-07-30 17:07:55 +0400 (Tue, 30 Jul 2013) | 5 lines

  Include an Accept header in requests.

  PR:             kern/180917
  MFC after:      1 week

Reviewed by:	des

git-svn-id: svn://svn.freebsd.org/base/stable/9@256267 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f