Hi,

Currently the 'mach' file of the disassemble_info struct initialized by 
cgen_disassemble is left with the default value of 0, which indicates to 
use the default bfd machine. This patch allows the specification of a 
bfd machine number, so that targets with multiple cgen MACHs can filter 
the insn set correctly when disassembling.

The machine number is an optional argument to 
cgen_bi_endian_cpu::disassemble with a default value of zero, to 
preserve the current behaviour in ports which don't use this feature. 
The machine number is then passed to cgen_disassemble which stores it in 
the disassemble_info for use by the disassembler. The machine number is 
also stored in the bfd_arch_hack struct by register_name and is compared 
against the requested machine number in bfd_lookup_arch.

This has been tested against an internal port which uses this feature 
and against xstormy16 which does not.

ok to commit?

Dave