The history of stdint.h ?

[walt]

I'm trying to debug the grub port, which fails with error messages
about previous definitions of things previously defined in stdint.h.
I see that stdint.h is defined in DFlyBSD and FBSD5, but not FBSD4.

So I assume that stdint.h was MFC'd from FBSD5 to DFly -- is this
right or wrong?
I also have read that stdint.h is part of gnu libc -- is this
right or wrong?  If so, why was it adopted as part of FBSD5 but
not FBSD4?
These are big questions and I'm sure they involve bikeshed-like
arguments -- but if someone could boil it down to newbie-like
basics I'd be grateful :o)
Thanks!