On several points on swupd we need to free a pointer and then set it to
NULL. This is made in some areas using the free_and_clear_pointer(). But
most places free_and_clear_pointer() is used, this is not really necessary.
On the other hand it's hard to make sure that we are really setting to NULL
every pointer that we need, so we're adding a more conservative approach on
setting every pointer to NULL after free using a wrapper.
The greatest advantage of this wrapper over free_and_clear_pointer() is that
it's not type dependent and we don't need to call it with a pointer of a pointer,
so calls look more to calls to a standard free.
Signed-off-by: Otavio Pontes <otavio.pontes@intel.com>
William Douglas