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

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

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

Add the Clang specific -Wmissing-variable-declarations to WARNS=6.

This compiler flag enforces that that people either mark variables
static or use an external declarations for the variable, similar to how
-Wmissing-prototypes works for functions.

Due to the fact that Yacc/Lex generate code that cannot trivially be
changed to not warn because of this (lots of yy* variables), add a
NO_WMISSING_VARIABLE_DECLARATIONS that can be used to turn off this
specific compiler warning.

Announced on: toolchain@

Stop calling _init/_fini methods from crt1 for dynamic binaries. Do
call preinit, init and fini arrays methods from crt1 for static binaries.

Mark new crt1 with FreeBSD-specific ELF note.

Move some common crt1 code into new MI file ignore_init.c, to reduce
duplication. Also, conservatively adjust nearby sources for style.

Reviewed by: kan
Tested by: andrew (arm), flo (sparc64)
MFC after: 3 weeks

Use default WARNS setting (of 6) for lib/csu.

PR: bin/140089
Reviewed by: jmallett
Approved by: ed (co-mentor)

Build lib/ with WARNS=6 by default.

Similar to libexec/, do the same with lib/. Make WARNS=6 the norm and
lower it when needed.

I'm setting WARNS?=0 for secure/. It seems secure/ includes the
Makefile.inc provided by lib/. I'm not going to touch that directory.
Most of the code there is contributed anyway.

Fix build when WITH_SSP is set explicitly.

Submitted by: Jeremie Le Hen

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>