MFC r232894:

MFC r232894:
  Pull in r145194 from upstream clang trunk:

    Make our handling of MMX x SSE closer to what gcc does:

    * Enabling sse enables mmx.
    * Disabling (-mno-mmx) mmx, doesn't disable sse (we got this right already).
    * The order in not important. -msse -mno-mmx is the same as -mno-mmx -msse.

  Some configure scripts depend on this.

  PR:		i386/165968

MFC r232933:
  Update comments and CFLAGS in sys/conf/kern.mk, introduced in r221879,
  to match reality: clang does _not_ disable SSE automatically when
  -mno-mmx is used, you have to specify -mno-sse explicitly.

  Note this was the case even before r232894, which only makes a change in
  the 'positive' flag case; e.g. when you specify -msse, MMX gets enabled
  too.

git-svn-id: svn://svn.freebsd.org/base/stable/9@233166 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f