[MLton] Shortening dependency chains in the x86 codegen

[Vesa Karvonen]

Quoting Florian Weimer <fw at deneb.enyo.de>:
> > Take a look at the following code for 32-bit endianness swapping
> > generated by MLton on x86:
> 
> I'm sure that nowaydays, you could just use bswapl.  It's available in
> i486 and up, and AFAIK, call compatibles in use today implement it.

Just to clarify, I wasn't suggesting the optimization for the sake
of optimizing endianness swapping.

-Vesa Karvonen