Don't assume that lib_common.h and libdeflate.h don't include
<stdlib.h>. Currently this change doesn't matter unless someone uses
-DFREESTANDING for a Windows build, which isn't supported anyway, but we
might as well clean this up.
Update https://github.com/ebiggers/libdeflate/pull/68
Allow building libdeflate without linking to any libc functions by using
'make FREESTANDING=1'. When using such a library build, the user will
need to call libdeflate_set_memory_allocator() before anything else,
since malloc() and free() will be unavailable.
[Folded in fix from Ingvar Stepanyan to use -nostdlib, and made
freestanding_tests() check that no libs are linked to.]
Update https://github.com/ebiggers/libdeflate/issues/62
In preparation for adding custom memory allocator support, don't call
the standard memory allocation functions directly but rather wrap them
with libdeflate_malloc() and libdeflate_free().
