mem: Don't use posix_memalign() and friends with custom wrapper

mem: Don't use posix_memalign() and friends with custom wrapper

If the application provides custom memory allocations functions via
CRYPTO_set_mem_functions() then those should be used instead something
else like posix_memalign(). The applications might verify alloc and free
calls and pointers from posix_memalign() were never returned by the
implementations.

At least stunnel4 complains here.

Use posix_memalign() or if aligned_alloc() only if the application did
not provide a custom malloc() implementation. In case of a custom
implementation use CRYPTO_malloc() and align the memory accordingly.

Fixes #25678

Signed-off-by: Sebastian Andrzej Siewior <sebastian@breakpoint.cc>
Reviewed-by: Saša Nedvědický <sashan@openssl.org>
Reviewed-by: Matt Caswell <matt@openssl.org>
Reviewed-by: Shane Lontis <shane.lontis@oracle.com>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/25682)