CFT: powerpcspe arch port

To anyone using the PowerPC e500v2 core, I have created a new
architecture port, powerpc.powerpcspe, which supports the use of the
Signal Processing Engine found in these SoCs.  It does not support
e500v1, which only has single-precision floating point capabilities.

It can be found at svn.freebsd.org/base/projects/powerpcspe .  It has
been tested on a RouterBoard RB800, where it boots to multiuser, and
some basic utilities have been run (ls, sh).

Please report any problems with it to me and ppc_at_.

- Justin