declare nios machine numbers

[Nick Clifton]

Hi Mike,

> i was playing around with the altera toolchain when i noticed they're using a 
> low EM_ number for their NIOS2 rather than a random 'safe' one ... so here's 
> two patches to add nios so someone else doesnt increment and collide

These patches are approved - please apply them, along with suitable 
ChangeLog entries (which really should have been included with the patch 
submission).

Cheers
   Nick