In `BKE_appdir.h`, include `<stddef.h>` as that defines `size_t`. This follows the "include what you use" principle, and makes it possible to use `BKE_appdir.h` without having to bother with its dependencies. No functional changes.
In `BKE_appdir.h`, include `<stddef.h>` as that defines `size_t`. This follows the "include what you use" principle, and makes it possible to use `BKE_appdir.h` without having to bother with its dependencies. No functional changes.