Instead of defining LITTLE_ENDIAN and BIG_ENDIAN ourselves, we should
use the definitions from the compiler.
Additionally, we don't have <bits/endian.h>, so it's never correct to
include that header.
These definitions appear to be unused and are not required by POSIX.
They appear to be specific to OpenBSD and do not seem to exist on any
other system.
We don't check for feature test macros in any other LibC header, and
especially not for _GNU_SOURCE or _BSD_SOURCE. With no feature test
macro defined, this header would previously essentially be empty.
POSIX doesn't seem to require any feature test macros for this header
either.
SPDX License Identifiers are a more compact / standardized
way of representing file license information.
See: https://spdx.dev/resources/use/#identifiers
This was done with the `ambr` search and replace tool.
ambr --no-parent-ignore --key-from-file --rep-from-file key.txt rep.txt *
Sönke Holz