2012/03/30 - Mark Hatle <mark.hatle@windriver.com>
  - Initial revision

There are 4 primary PowerPC ABIs.
# *) Hard/Soft Floating Point
# *) 32-bit/64-bit

TUNE_ARCH is defined as either "powerpc" or "powerpc64" based on the m32 
or m64 feature.

May of the PowerPC package archictures are based on legacy Linux names.
However, a general naming scheme should be similar to: ppc[64][<family>][-nf].
(Note: the default package architectures are "powerpc" and "powerpc64".)

TUNE_PKGARCH is defined as TUNE_PKGARCH:tune-${DEFAULTTUNE}.  All 
PowerPC tunings are required to define TUNE_PKGARCH:tune-<tune>.