lib/memalign: remove smalloc()/sfree() dependency

lib/memalign: remove smalloc()/sfree() dependency

fio_memalign()/fio_memfree() implementation shouldn't depend on
smalloc()/sfree() which has dependency on fio code itself.
e.g. This forces unittest code to prepare stab functions for
smalloc()/sfree().

This smalloc()/sfree() dependency was added by 3114b675fd
("fio: enable cross-thread overlap checking with processes").

Rename fio_memalign()/fio_memfree() to __fio_memalign()/__fio_memfree()
and take a function pointer instead of a boolean flag.
Add fio_memalign()/fio_memfree() as an inlined wrapper for
__fio_memalign()/__fio_memfree() without API change.
The only real change here is lib/memalign functions got renamed.

Signed-off-by: Tomohiro Kusumi <kusumi.tomohiro@gmail.com>