Multi-arch and user-control of architecture flags

[Andrew Cagney]

>   /* Add root prefix command for all "set mips"/"show mips" commands */
>   add_prefix_cmd ("mips", no_class, set_mips_command,
>                   "Various MIPS specific commands.",
>                   &setmipscmdlist, "set mips ", 0, &setlist);
> 
>   add_prefix_cmd ("mips", no_class, show_mips_command,
>                   "Various MIPS specific commands.",
>                   &showmipscmdlist, "show mips ", 0, &showlist);
> 

Just a PS on this.  The command set ``set mips fpu ...'' et.al. isn't 
perfect - it sets a global for all mips which is probably sufficient for 
what people want.

Eventually a per thread command may be needed.   So that a target 
containing an 8086 and x86-64 can have, separatly, their disassembly 
mode.  Something like:

	thread 5 set i386 disassembler x86-64

(just ignore the syntax though).  However, not our problem :-)

Andrew