[MLton] runtime optimization flags?

[Matthew Fluet]

>>> I also have a few minor makefile suggestions, but I will bring those up
>>> in a separate message.
>>
>> Please do.
>>
>
> Ok. Two things:
>
> 1. GNU Make gives us 2 kinds of variables, and I think the MLton
> makefiles are using the sub-optimal kind:
> http://www.gnu.org/software/make/manual/html_node/Flavors.html
...
> Patch 1 replaces all instances of plain old "=" with ":=", except in
> packages/freebsd/Makefile since I have no way of testing it.
>
> 2. bytecode/Makefile is missing the TARGET_OS variable. This could cause
> the build to fail strangely when not building from the toplevel Makefile
> (which exports TARGET_OS). runtime/Makefile correctly defines this
> variable. This is fixed in patch 2, to be applied after patch 1.

I've applied both patches to trunk.  Thanks for putting them together.