Just like Dr. POSIX ordered. Move the macro where it belongs, but make
sure it's visible to Userland files compiled with -DKERNEL. Parts of
LibEDID that are compiled into the Kernel use offsetof to parse the
EDID information given to us by hardware.
POSIX doesn't tell us to export a macro like this, and it's largely
going to never be defined when compiling a serenity-native C++ file,
since AK defines it already.
This does raise a strange issue where some futex-related helpers in
serenity.h are declared with ALWAYS_INLINE. Whether these helpers belong
in a C-visible header as file-static methods is questionable, but let's
work around the issue but adding some preprocessor magic to make sure
these declarations get the behavior they used to have without leaking
macros.
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 *
