aarch64_opcode_table changes for BZ 19722

[Nick Clifton]

Hi Szabolcs,

> with the new verifier field some
> 
>  {a,b,c,d},
> 
> table entries were changed to
> 
>  {a,b,c,d,NULL},
> 
> others to
> 
>  c_INS(a,b,d),
> 
> the goal of those c_INS macros is not clear to me,
> is it just to align the opcode table columns?

No - it was to make future changes to the table easier to do and
to make the verifier functions stand out.

My original idea was that I would use macros for every entry, 
since I thought that a lot of the fields we duplicated in every 
entry.  Of course this turned out to be incorrect and I soon
realised that I would need too many macros, and that the macros
would not make anything clearer.  So instead I decided to use
macros just for the common cases - where the fields are 
duplicated - and to use explicit initialisation for the 
"interesting" instructions.  This also meant that it would be
easy to find which instructions had verifiers and which did not.

Cheers
  Nick