[RFC] Merge mkimage tool

[Josh Boyer]

The following patches merge the mkimage tool into the kernel.  For now,
this is just an RFC, which is why I'm only posting it here.  If enough
people agree that this is a good idea, then I'll post it to LKML.  Note
that mkimage is always generated.  It should probably only be built for
platforms that need it, but I didn't figure out how to do that yet.

This is currently based on the mkimage version found in U-Boot 1.3.1.

Comments, flames, suggestions, insults, monetary donations welcome.

josh