aligned_alloc() is implemented in terms of posix_memalign() which is
only declared in <stdlib.h> but not defined in Newlib in general. At
least Linux and RTEMS implement this function.
newlib/ChangeLog
2015-10-14 Sebastian Huber <sebastian.huber@embedded-brains.de>
* libc/stdlib/Makefile.am (GENERAL_SOURCES): Add
alloc_aligned.c.c.
* libc/stdlib/Makefile.in: Regenerate.
* libc/stdlib/aligned_alloc.c: New.
Sebastian Huber