[Bug 20474] Wine can't be built with GCC in C99 mode

https://bugs.winehq.org/show_bug.cgi?id=20474

--- Comment #17 from Saulius K.  ---
(In reply to André H. from comment #16)
> I think we are supposed to use a gnu standard, most popular software won't
> work with pure c standard afaik.
> Last time I tested gnu89, gnu99 and gnu11 worked.

André, how does using gnu standard relate to this statement, please?
https://wiki.winehq.org/Code_Hygiene#Constants_as_Character_Arrays

--- snip ---
but it keeps the code standards-compliant and portable across build
environments.
--- snap ---

I think the project needs to express definition of the portability in direct
way which I was unable to find online ATM.  Any pointers?