MFC Loader Fixes 2017q4p4: r324552,r324553,r324554,r324555,r324556
r324552: Kill the userboot copy of libstand.
r324553: Rename libstand.a to libsa.a and libstand32.a to libsa32.a
r324554: Move crc32.c, util.c and gpt.c over to libsa.
r324555: Honor CFLAGS modifications in Makefile.inc by using += here.
r324556: Move ufsread.c