PowerPC G4 support

[Till Straumann]

Hi all.

Is somebody already working on adding G4
support? If not, I could provide a rudimentary
implementation:

 - CPU version recognition etc.
 - cache initialization.
 - save/restore AltiVec context.

Are there suggestions regarding the
implementation of the vector context
save/restore, i.e. should this go to
the core code or should it be a user
extension?

Something else that bothers me are the definitions

#define _IO_BASE        PREP_ISA_IO_BASE
#define _ISA_MEM_BASE   PREP_ISA_MEM_BASE
#define PCI_DRAM_OFFSET PREP_PCI_DRAM_OFFSET

found in lib/libcpu/powerpc/shared/include/io.h

This should be the business of the BSP rather than
the CPU library's!

-- Till