sim/ppc PAGE_SIZE redefinition

[CHIGOT, CLEMENT]

> > I'm not able to build "sim/ppc" anymore on AIX.
> 
> The sim sources are part of gdb, not the binutils ...

Oh, I wasn't aware of that. 
Note that it's still being built even when --disable-gdb is provided 
to the configure.  

>> or is it safe to
>> rename it PAGE_SIZE_1k or something like that ?
>
> It really depends upon how the simulator sources are going to use the constant.
> But it would probably be best if the value used inside the simulator matched
> the system value.  That way you are unlikely to run into host-vs-sim emulation
> issues.  All of which is a fancy to way to say that the best solutions is
> probably to patch semantics.h to only define PAGE_SIZE if it is not already
> defined.

That's what I've done locally. But I don't know anything about sim. The tests 
on AIX aren't even building. On linux/ppc64le, it seems ok though. I can 
submit the patch, but I want to be sure that this is the correct way to fix that.

Thanks,
Clément