When ffi.new() is used to build a new pointer object, the returned
pointer object has ownership on the allocated memory. When it is
garbage-collected, then the memory is freed. Thus, we need to make sure
the original object survives its use, otherwise the casted pointer will
point to garbage.
This fixes one test which was failing with the latest CFFI version, see
issue #694. Thus, this commit also reverts 803b1cb (cffi 1.10 not yet
supported, 2017-03-22) where the latest CFFI version was marked as
unsupported.
Signed-off-by: Lukas Fleischer <lfleischer@lfos.de>