[ccan] ccan and C standards newer than gnu89

[Cody P Schafer]

I while back, I submitted a module that depended on some c99 behavior
(inline & extern inline) that isn't quite avalaible in gnu89, and as a
result was rejected at the time.

Now that gcc has switched it's default to gnu11 (which includes the
behavior of inline & extern inline I needed), I'm wondering if modules
that need non-gnu89 features might be submittable.