MFC r228558, r228585, r228588, r228652, r228707:

MFC r228558, r228585, r228588, r228652, r228707:

  Unfortunately, clang gives warnings about sendmail code that cannot be
  turned off yet.  Since this is contrib code, and we don't really care
  about the warnings, just make them non-fatal for now.

MFC r228590:

  Fix typos in the comments about clang warnings in several
  sendmail-related Makefiles.

  Spotted by:	arundel

MFC r228708:

  In usr.bin/vacation/Makefile, fix a typo in the comment about clang
  warnings.

  Spotted by:	arundel

git-svn-id: svn://svn.freebsd.org/base/stable/9@229112 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f