gcc-7-arm vendor branch

[Pop, Sebastian]

Hi,
I would like to thank David Edelsohn for his help during the process of
getting Amazon’s contributions to GCC covered by an FSF copyright assignment.

As a first contribution, I would like to create a vendor branch for gcc-7
that will contain back-ported patches for Arm such as -moutline-atomics flag
and missing NEON intrinsics.
The branch will facilitate integration of these important changes in systems
such as Ubuntu 18.04 and Amazon Linux 2 that are still relying on gcc-7.
I will ask reviews and recommendations from Arm maintainers for the patches
to be integrated in the gcc-7-arm branch.

Thanks,
Sebastian