x86 makefile unification and cleaning

Since first posting I have updated the patch like this:
o Fixed a few bugs shown up by more extensive testing
o Avoided one ifdef group
o Added a few more comments
o Removed and/or updated a few comments

On top of that I did a few more patches:

Sam Ravnborg (5):
x86: unification of arch/x86/Makefiles
x86: share more options between 32 and 64 bit build
x86: biarch support for 32 bit builds beautified
x86: teach vdso to clean
x86: teach vdso to clean

The resulting diffstat:

 arch/x86/Makefile      |  244 +++++++++++++++++++++++++++++++++++++++++++++++-
 arch/x86/Makefile_32   |  181 -----------------------------------
 arch/x86/Makefile_64   |  141 ----------------------------
 arch/x86/boot/Makefile |    4 +-
 arch/x86/vdso/Makefile |    2 +
 5 files changed, 243 insertions(+), 329 deletions(-)

I'm pretty satisfied with the result.
But I hope someone can look into the cpu specific stuff and merge the remaining bits from 64 bit to the currently 32 bit only Makefile_32.cpu file.

This will benefit readability and UML I think.

The patches are made on top of the mm branch of the x86 tree.

Patches follows.

Sam