yocto-kernel: factor common routes, update to 2.6.37 and branch renaming

yocto-kernel: factor common routes, update to 2.6.37 and branch renaming

In order to extend and create more kernel recipes based on the
supported yocto kernel common routines need to be placed in
re-usable blocks.

To accomplish this meta/recipes-kernel/linux/linux-yocto_git.bb
is broken into three parts:

 - meta/classes/kernel-yocto.bbclass: contains common routines
   for checking out and configuring a yocto kernel git repository.
   This should be inherited by recipes that need this functionality.

 - meta/recipes-kernel/linux/linux-yocto.inc: Contains the machine
   mappings, compatibility, build directives and common task
   definitions for a yocto kernel based recipe. This inherits
   kernel-yocto, and is the typical point of entry for other recipes.

 - meta/recipes-kernel/linux/linuux-tools.inc: tasks and function definitions
   for kernel recipes that want to build/export perf

It also updates the linux-yocto recipe to default to 2.6.37.

As part of the update to 2.6.37 the branch naming and conventions
have been modified to show inheritance, and be more generic.

For example:

  master
  meta
  yocto/base
  yocto/standard/arm_versatile_926ejs
  yocto/standard/base
  yocto/standard/beagleboard
  yocto/standard/common_pc/atom-pc
  yocto/standard/common_pc/base
  yocto/standard/common_pc_64
  yocto/standard/fsl-mpc8315e-rdb
  yocto/standard/intel_atom_z530
  yocto/standard/intel_core_qm57_pch
  yocto/standard/mti_malta32_be
  yocto/standard/preempt_rt/base
  yocto/standard/preempt_rt/common_pc
  yocto/standard/preempt_rt/common_pc_64
  yocto/standard/preempt_rt/intel_atom_z530
  yocto/standard/preempt_rt/intel_core_qm57_pch
  yocto/standard/qemu_ppc32
  yocto/standard/routerstationpro

In this structure:

  master: tracks the mainline kernel
  meta: meta information for the BSPs and kernel features
  yocto/base: baseline kernel branch
  yocto/standard/base: 'standard' kernel, contains features
                        and configs for all BSPs
  yocto/standard/<machine>: represents a BSP with specific
                            features or configurations

The tools, tree and libc-headers have all been updated to
deal with this new structure. Also in addition to dealing with
the new structure, they continue to work with the existing
tree and will adapt at runtime to the differences.

The linux-yocto-stable_git.bb recipe continues to build the
2.6.34 based tree,and linux-yocto_git.bb builds 2.6.37. As
boards are enabled for the new kernel they will move from
-stable to the development kernel. As of now, only the
emulated targets have moved to 2.6.37-rcX

Signed-off-by: Bruce Ashfield <bruce.ashfield@windriver.com>