libc/arch-arm/bionic/memcpy.a9.S: memcpy from cortex-strings.

This memcpy code uses NEON/VFP to achieve very good performance
on ARMv7-A processors. It is specifically tuned for A15 but should
provide good performance on A9 also. It is equivalent to the code
in cortex-strings rev 116.

This patch is a follow up the existing gerrit change:

I7f6f77995f3ca903ad9c66d14261441667a2a935

This version includes a tweak for performance on misaligned
buffers and splits the header comment into license and
documentation sections.

Change-Id: Ibd2e23c8d8e01357ba0247be1d05192de3ceba69
Signed-off-by: Will Newton <will.newton@linaro.org>

Conflicts:
	libc/NOTICE
Make bionic's <netinet/icmp6.h> standalone, like glibc's.

This removes the need for a bionic-specific hack in external/iproute2.

Bug: 9671560
Change-Id: I9f15be0711d26bca863bd66be9a39606500fb948
Remove <netinet/icmp6.h> ni_* macros.

glibc doesn't have these, and they prevent ping from building out of
the box because it assumes it can define them.

Bug: 9671560
Change-Id: I815f2a9c4fd96a0ea2952eb5a71ddf51e0763660