PATCH: Support MIPS II

[Benjamin Kosnik]

one file:
> #ifndef _BITS_ATOMICITY_H
>
> #ifdef _MIPS_ISA
>
> #include <sgidefs.h>

second file:
> #if _MIPS_ISA >= _MIPS_ISA_MIPS2
>
> #define _BITS_ATOMICITY_H 1
>
> asm for MIPS 2.
>
> #endif /* _MIPS_ISA >= _MIPS_ISA_MIPS2 */
>
> #endif /* !_MIPS_ISA */
>

generic file:
> #ifndef _BITS_ATOMICITY_H
>
> #define _BITS_ATOMICITY_H 1
>
> generic version
>
> #endif
>

see how i386/i486 are done.

-benjamin