arch: Fix all override related warnings.

Clang has started(?) reporting override related warnings, something gcc
apparently did before, but was disabled in the SConstruct. Rather than
disable the warnings in for clang as well, this change fixes the
warnings. A future change will re-enable the warnings for gcc.

Change-Id: I3cc79e45749b2ae0f9bebb1acadc56a3d3a942da
Reviewed-on: https://gem5-review.googlesource.com/9343
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Maintainer: Gabe Black <gabeblack@google.com>

includes: sort all includes

Make commenting on close namespace brackets consistent.

Ran all the source files through 'perl -pi' with this script:

s|\s*(};?\s*)?/\*\s*(end\s*)?namespace\s*(\S+)\s*\*/(\s*})?|} // namespace $3|;
s|\s*};?\s*//\s*(end\s*)?namespace\s*(\S+)\s*|} // namespace $2\n|;
s|\s*};?\s*//\s*(\S+)\s*namespace\s*|} // namespace $1\n|;

Also did a little manual editing on some of the arch/*/isa_traits.hh files
and src/SConscript.

POWER: Add support for the Power ISA

This adds support for the 32-bit, big endian Power ISA. This supports both
integer and floating point instructions based on the Power ISA Book I v2.06.