[ccan] ccan and C standards newer than gnu89

[Cody P Schafer]

>>> It *can* generally be made built time configurable, but it usually
>>> requires ugly macros scattered in an unpleasantly large number of
>>> locations.
>>
>>
>> That sounds unpleasant.  Perhaps we publicise a version or tag of ccan that
>> is "old compiler compliant" and people just pull that older version.  If
>> it's missing functionality they require from later ccan versions, their
>> backport patches are welcome :)
>>
>
> When I first tried to get the module in question merged (which needed
> c99-inline), after the initial rejection I looked at adding a
> configurator test for the style of inline supported. Unfortunately, I
> couldn't find a way to check the style of inline without needing to
> build more than 1 source file (and then link them together), which
> would have required more restructuring to configurator than I was
> willing to do.

I suppose a workaround here would be to probe some defines (like the
STDC_VERSION one) to avoid needing to change configurator too much.
Perhaps that probing could even be done directly in an "inline"
module.