sparc64 support for Solaris

[Joe Buck]

> I was wondering how I can enable 64 bit support and v9 instruction
> scheduling for an Ultra 1 Model 170 running Solaris2.5.  This is
> apparently not possible when the target is "sparc-sun-solaris2.5.1".

If you turned it on, your process would bomb at the first context switch.
Solaris 2.5.x does not save the 64-bit register state, so basically some
registers will come back randomized (from other processes?).

Solaris 2.6 is supposed to fix this.  Also, HAL/OS, HAL's patched
version of Solaris 2.4, fixes it.  So please don't turn it on on 2.5.1
(unless you are cross-compiling).  Very bad things will happen.