Port lib/libc/ssp to FreeBSD

In most cases, the buffers and data were resized, but when dealing with the
helpers, some of the code was adjusted to fail more reliably

Submitted by: pho
rpc_control on FreeBSD is a public-ish API (not prefixed with __), not private
like NetBSD

Submitted by: pho
Add key+=append syntax to sysrc(8).

Reviewed by:	shurd
MFC after:	3 days
X-MFC-to:	stable/10 stable/9
Finish off lib/libc/stdlib/t_strtod.c port by checking for "y" twice on
FreeBSD, and always assume long long double exists on FreeBSD

Submitted by: pho
Follow-up to r255036; remove beforeinstall directives from bsdconfig(8)
Makefile's, fixing concurrent installworld (`make -j17 installworld').

Thanks to:	delphij, emaste
Reviewed by:	delphij
MFC after:	3 days
X-MFC-to:	stable/10, stable/9
Add Makefile snippet to ease porting NetBSD testcases to FreeBSD from
contrib/netbsd-tests

This Makefile snippet handles polluting testcases with -lnetbsd, specific
headers for ATF version differences, and does necessary rewriting for the
testcases to match the format discussed on the TestSuite wiki page
(t_<foo> -> <foo>_test)

One must define SRCTOP (inspired by projects/bmake), OBJTOP, and TESTSRC
(e.g. contrib/netbsd-tests/lib/libc/gen) to use the Makefile snippet

Test programs are specific either via NETBSD_ATF_TESTS_C or NETBSD_ATF_TESTS_SH

C++ analogs aren't currently implemented.

The imported testcases will be cleaned up to use this Makefile snippet pseudo
"API".
Add reachover Makefiles for contrib/netbsd-tests/lib/libc; this adds approximately
500 new testcases

Various TODOs have been sprinkled around the Makefiles for items that even need
to be ported (missing features), testcases have issues with building/linking, or
issues at runtime.

A variant of this code has been tested extensively on amd64 and i386
10-STABLE/11-CURRENT for several months without issue. It builds on other
architectures, but the code will remain off until I have prove it works on
virtual hardware or real hardware on other architectures

In collaboration with: pho, Casey Peel <casey.peel@isilon.com>
Sponsored by: EMC / Isilon Storage Division
Improve the ability to cancel an in-flight request by using an
interrupt, via SIGCONT, to force the read or write system call to
return prematurely.

Reviewed by:	grehan
As an optimization (in simple, well used cases) only call cat ${.ALLSRC} when
generating files from various sources instead of calling cat ${.ALLSRC} | sed

The perl case was skipped because it's not being used in the tree at this time
Commit missing header for sys/time.h compat on NetBSD to unbreak the amd64/i386
build

Pointyhat to: me (forgot to svn add it sooner)