Also include the possibility to include reports modifying existing external documentation.
Current version doesn't unbreak memalign consumers unless <malloc.h> has something like #define memalign aligned_alloc. If fixed then FreeBSD could take advantage of musl support in various projects. ;)
This is not true implementation of memalign(3). memalign accepts any size argument, while both posix_memalign() and aligned_alloc() require size to be multiple of the alignment.
Looks OK. From my ports/ experience the header is often used when either <stdlib.h> is enough, for memalign or for malloc_usable_size.
I have been begging for this for years and strongly support.