Merge branch 'core/documentation' of git://git.kernel.org/pub/scm/linux/kernel/git...

A week late but I managed to complete it all and moved it into Git, for better
structure and easy pulling.

Changes relative to the last submission:

  - Added higher level subsystem directories to collect features by
    subsystem:

      triton:~/tip> ls Documentation/features/
      arch-support.txt  core  debug  io  lib  list-arch.sh  locking  perf  sched  seccomp  time  vm

    each subsystem directory contains the feature directories. For example locking
    has:

      triton:~/tip> ls Documentation/features/locking/
      cmpxchg-local  lockdep  queued-rwlocks  queued-spinlocks  rwsem-optimized

    It's all pretty straightforward to navigate. Advantages are better
    visualization, plus git log is able to list changes per subsystem.

  - Prettified the visualization some more.

  - Improved/corrected the support matrices based on feedback to earlier submissions.

  - Updated the support matrices to today's linux-next, so that by the time this
    shows up in upstream in the next merge window it's really recent.
    Most notably there's a new architecture in linux-next (h8300).

This structure should address all feedback that I got and should minimize the
maintenance overhead (chance of conflicts).