[m-rev.] for review: add a builtin unsigned word sized integer type -- Part 1

[Julien Fischer]

Hi Sebastian,

On Mon, 24 Oct 2016, Sebastian Godelet wrote:

>> I won't commit this until I've finished part 2 of this change and posted
>> that for review.  Once it is committed everyone will need to update
>> their installed compilers before part 2 is commited.
>>
> Can I use a recent compiler to compile this commit or would I have to re-bootstrap?

Part 1 of this change can be compiled by any recent compiler.  Part 2
(which I will hopefully post for review tomorrow) will require a
bootstrap compiler that includes part 1.  I wouldn't bother doing
anything with either of them until they've been reviewed and ROTDs
containing them are available.

> This change does not cover anything along the lines of exposing
> int32_t and the likes to the C backend, right?

No, this change introduces word sized unsigned integer types.  In C
grades, they map on to the runtime's existing MR_Unsigned type.

There was a discussion in the thread titled "undefined behaviours in
int.m" about adding fixed size unsigned types.  If / when they're added
then int32 will map on to int32_t in C grades.

> Now that we can require C99, that means we can also make use of
> <inttypes.h>, or is that an not always the case?

More strictly we're going to require a subset of C99 (since not
all C compilers support all of it), however inttypes.h and stdint.h
will be part of that required subset.

Julien.