MFC r272389:

Diff reduction with kernel code: instruct the compiler that the data of
these types may be unaligned to their "normal" alignment and exercise
caution when accessing them.

PR:		194071
MFC r270183:

  Avoid showing stale errors when nmount(2) fails.
MFC r271321:

  Don't cross mount boundaries when cleaning tmp files.

Relnotes:	yes
MFC r272028:

  Make it more explicitly clear that -t will not change filename.
MFC r271720:

  If fgets(3) fails in getbounds(), show strerror(3) if not an EOF. Also fix a
  FILE* leak in getbounds().

PR:		192032