Copy stable/10@r272459 to releng/10.1 as part of
the 10.1-RELEASE process.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

MFC r257532 (by adrian):

Fix this build for clang.

MFC r259730:

To avoid having to explicitly test COMPILER_TYPE for setting
clang-specific or gcc-specific flags, introduce the following new
variables for use in Makefiles:

CFLAGS.clang
CFLAGS.gcc
CXXFLAGS.clang
CXXFLAGS.gcc

In bsd.sys.mk, these get appended to the regular CFLAGS or CXXFLAGS for
the right compiler.

MFC r259913:

For libstand and sys/boot, split off gcc-only flags into CFLAGS.gcc.

MFC r259927:

Fix pc98 build, by also forcing COMPILER_TYPE in sys/boot/pc98/boot2's
Makefile.

Pointy hat to: dim

Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

cosmetic changes to reduce diffs against i386.

MFi386: r241785

boot: use -march=i386 for both i386 and amd64 builds

On i386 and amd64, consistently use the following options whenever we
want to avoid using any "advanced" CPU features:

-mno-mmx -mno-3dnow -mno-sse -mno-sse2 -mno-sse3 -msoft-float

Don't use 15M-16M area on pc98. It's reserved for some devices.

MFC after: 2 week

MFi386:

Move the loader's entry point to 0x200000. This change is also needed
for pc98.

MFC after: 3 days

Enable GCC stack protection (aka Propolice) for userland:
- It is opt-out for now so as to give it maximum testing, but it may be
turned opt-in for stable branches depending on the consensus. You
can turn it off with WITHOUT_SSP.
- WITHOUT_SSP was previously used to disable the build of GNU libssp.
It is harmless to steal the knob as SSP symbols have been provided
by libc for a long time, GNU libssp should not have been much used.
- SSP is disabled in a few corners such as system bootstrap programs
(sys/boot), process bootstrap code (rtld, csu) and SSP symbols themselves.
- It should be safe to use -fstack-protector-all to build world, however
libc will be automatically downgraded to -fstack-protector because it
breaks rtld otherwise.
- This option is unavailable on ia64.

Enable GCC stack protection (aka Propolice) for kernel:
- It is opt-out for now so as to give it maximum testing.
- Do not compile your kernel with -fstack-protector-all, it won't work.

Submitted by: Jeremie Le Hen <jeremie@le-hen.org>

Optimize for size on pc98. It enables to boot a kernel again.

I don't know what's wrong (loader, boot2 or others), but this change is
effective.

Tested by: NAKAJI Hiroyuki
MFC after: 3 days

MFi386: revisions 1.10 and 1.11.
- Add '-mno-mmx -mno-3dnow -mno-sse -mno-sse2 -mno-sse3' to CFLAGS.

MFi386: Factor out -nostdlib and use PROG.

MFi386: Cleanups to sys/boot makefiles.

Add -ffreestanding to CFLAGS.

Merged from sys/boot/i386/Makefile.inc revision 1.2.

Synced with following files:
src/sys/boot/i386/Makefile.inc 1.1
src/sys/boot/i386/btx/btx/btx.s 1.15
src/sys/boot/i386/btx/btxldr/Makefile 1.8
src/sys/boot/i386/btx/btxldr/btxldr.s 1.9
src/sys/boot/i386/libi386/biosdisk.c 1.29
src/sys/boot/i386/loader/Makefile 1.42
src/sys/boot/i386/loader/main.c 1.18
(entry point address of loader was not changed.)

Reviewed by: nyan