Machine setting on disassembly

[Patrick Macdonald]

Hi,

We currently use CGEN_COMPUTE_ISA (cgen-dis.in) for target
isa selection on disassembly and I'd like to add
CGEN_COMPUTE_MACH for target machine selection (I have 
multiple machines under one architecture that can switch on
the fly).  

Anyone have moral/technical objections to allowing target
specific machine selection?  If not, I'll submit the patch
after testing.

Patrick