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

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

Add compiler support for the ARM EABI.

ARM EABI support is disabled by default and can be enabled by setting
WITH_ARM_EABI when building, however only the kernel-toolchain target will
work with this flag until the rest of the support is added.

Compile libgcov without stack protection. It can be linked into
both static and dynamic binaries compiled with or without stack
protection and should not depend on libssp_nonshared.a symbols.

Discussed with: kib
PR: bin/139052

Compile static gcov library with -fPIC to match what stock GCC builds
are doing. This is required for libgcov.a to be usable on amd64.

Reported by: stas

Update bmake glue to build GCC 4.2.

Also:
Switch FreeBSD to use libgcc_s.so.1.

Use dl_iterate_phdr to locate shared objects' exception frame
info instead of depending on older register_frame_info machinery.
This allows us to avoid depending on libgcc_s.so.1 in binaries
that do not use exception handling directly. As an additional
benefit it breaks circular libc <=> libgcc_s.so.1 dependency too.

Build newly added libgomp.so.1 library, the runtime support
bits for OpenMP.

Build LGPLed libssp library. Our libc provides our own
BSD-licensed SSP callbacks implementation, so this library
is only built to benefit applications that have hadcoded
knowledge of libssp.so and libssp_nonshared.a. When linked
in from command line, these libraries override libc
implementation.

Convert NO_PROFILE and NO_LIB32 to new style.

NODOCCOMPRESS -> NO_DOCCOMPRESS
NOINFO -> NO_INFO
NOINFOCOMPRESS -> NO_INFOCOMPRESS
NOLINT -> NO_LINT
NOPIC -> NO_PIC
NOPROFILE -> NO_PROFILE

For variables that are only checked with defined(), don't provide
any fake value.

Add libgcov, a runtime support library for binaries compiled for basic
block profiling.