MFC r261591 (nwhitehorn):

  Make libstand setjmp work for both 64- and 32-bit ABIs.
r261567: Build a 32-bit libstand under sys/boot/

  A 32-bit libstand is needed on 64-bit platforms for use by various
  bootloaders.  Previously only the 32-bit version was built, installed
  as /usr/lib/libstand.a.

  A new 64-bit libstand consumer will arrive in the near future, so move
  the bootloader-specific 32-bit version to sys/boot/libstand32/.

  Explicitly link against this version in the 32-bit loaders.

r261614: Build a 32-bit libstand under sys/boot/ for ppc64

  This change is equivalent to r261567 for i386/amd64.

Relnotes:	Yes
Sponsored by:	The FreeBSD Foundation