arch, base, cpu, dev, mem, sim: Remove #if 0-ed out code.

This code will be preserved through version control, but otherwise
creates clutter and will rot in place since it's never compiled.

Change-Id: Id265f6deac445116843956ea5cf1210d8127274e
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/18608
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Reviewed-by: Brandon Potter <Brandon.Potter@amd.com>
Maintainer: Jason Lowe-Power <jason@lowepower.com>
Tested-by: kokoro <noreply+kokoro@google.com>

style: Make a style pass over the whole arch/alpha directory.

style: Remove non-leading tabs everywhere they shouldn't be. Developers should configure their editors to not insert tabs

Updated Authors from bk prs info

New directory structure:
- simulator source now in 'src' subdirectory
- imported files from 'ext' repository
- support building in arbitrary places, including
outside of the source tree. See comment at top
of SConstruct file for more details.
Regression tests are temporarily disabled; that
syetem needs more extensive revisions.

SConstruct:
Update for new directory structure.
Modify to support build trees that are not subdirectories
of the source tree. See comment at top of file for
more details.
Regression tests are temporarily disabled.
src/arch/SConscript:
src/arch/isa_parser.py:
src/python/SConscript:
Update for new directory structure.