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

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

Merge binutils 2.17.50 to head. This brings a number of improvements to
x86 CPU support, better support for powerpc64, some new directives, and
many other things. Bump __FreeBSD_version, and add a note to UPDATING.

Thanks to the many people that have helped to test this.

Obtained from: projects/binutils-2.17

In fact, we don't need any of these __DYNAMIC. it is a.out leftover and commented out.

Use the same SEARCH_DIR as other platforms.

Add kernbase symbol and use it instead of magic numbers in the
linker script.

Add code model medlow to cflags and move the kernel load address from
just before the memory hole to 4 megs. Special case building exception.s
like locore.s, it needs to at the beginning so the branches out from the
trap table don't overflow.

Add a Makefile, ldscript, and config magic for sparc64. This is tailored
to build with a cross compiler alongside the standard compiler; it would be
more desirable to build in a chroot.