Detail and begin the arm64/aarch64 port in Ubuntu

Topics:
 - Compiler changes
 - Target compiler version and Linaro GCC release
 - Cross build support with multi-arch
 - Arch bootstrap
 - ARM Fast Models as builders
 - Expected Qemu support

Wookey has done some work on multi-arch cross building and bootstrapping of aarch64. Results quite positive but there is still a a fair amount of breakage from failed apt-get build-dep -aaarch64, no qemu to gloss over other cross issues and apt not knowing about staged/bootstrap build resolving.

Cross buildd results for Quantal: http://people.linaro.org/~wookey/buildd/quantal/sbuild-ma/status.html

Toolchain patches for gcc-4.7 by end of month(ish), kernel patches in a similar timeframe

dpkg architecture will be "arm64", GNU triplet is aarch64-linux-gnu

Real/virtualized hardware support:
 - Qemu is going to take a while, probably in the end of the year
 - Instruction set documentation public when?
 - Real hardware is probably just next year
 - Meanwhile we could debootstrap and even run armv8 code using ARM Fast Model, which Linaro should have available soon: http://www.arm.com/products/tools/models/fast-models.php

Fast Models:
 - Linaro can probably make it available for Ubuntu/Debian developers once we get it working internally
 - That can be useful for debootstrap at least
 - It could even be used as a builder, but it's very very slow (so probably a no-go)

Cross build support:
 - We need fixes for packages that "depends" on qemu
 - Multiarch dependency fixes for many packages. Perl and python are big blockers
 - Fixing arch-depending config-scripts in -dev packages

Initial list of packages to cross build/bootstrap:
 - C toolchain and {build-,}dependencies
 - Packaging toolchain (dpkg, apt, debhelper, etc) and dependencies

Wookey's public status of issues here: https://wiki.linaro.org/Platform/DevPlatform/CrossCompile/MultiarchCrossBuildStatus
Bootstrap: http://people.linaro.org/~wookey/buildd/quantal/sbuild-ma/status-bootstrap.html
[wookey] "status is very broken right now" (April 2012)
[wookey] "Status looking much brighter" (September)

http://bugs.debian.org/661538 - dpkg support for staged builds
http://bugs.debian.org/661537 - apt support for staged builds

Multiarch python: http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=683755
Multiarch perl: 'ntyni/multiarch-5.14' branch of git://git.debian.org/perl/perl.git

Work items:
[wookey] add arm64 arch to dpkg: DONE
[cjwatson] review xdeb staged patch: DONE
[steve-mcintyre] add the multiarch triplet to wiki.debian.org/Multiarch/Tuples: DONE
Get perl multiarched: DONE
Get python multiarched: DONE
[adconrad] Scour the archive for armel/armhf in debian/* and prep for arm64: TODO
[adconrad] add arm64 to Packages-arch-specific: DONE
[adconrad] backport arm64 dpkg support to lucid-cat: DONE
[adconrad] backport arm64 dpkg support to precise-updates: DONE