Record-only merges of recent loader fixes

Loader fixes were recently effectively MFC'd in r327942, r327944, r327945,
and r327957. These were all direct commits to stable/11 due to restructuring
in -HEAD where libstand and sys/boot are concerned, but achieve the same
effect as this range of commits.

Catch up on svn:mergeinfo following these, as this was missed in the
original commits to stable/11.