RFC: split ColdFire from m68k backend

[Kazu Hirata]

Hi Giovanni,

> > One thing that would be nice to have is to convert the
> > prologue/epilogue to RTL.

This sounds like a good idea.

> Also, m68k is the major cc0 target at the moment. Making it drop cc0 support
> would help cleaning up the compiler. You can ask Kazu Hirata, as he lately
> modified h8300 to drop cc0.

As Paolo pointed out, I have not checked in this change.  I am
thinking about doing so after the tree-ssa merge, provided that
somebody will review my middle-end patches that aim at preserving the
code quality when the h8300 port moves from cc0 to MODE_CC.

By the way, I am wondering if there is anybody out there testing the
m68k port on some kind of simulator.  Without that, making a large
change to the port would be very difficult.

Kazu Hirata