Array struct members were ignored by SWIG binding generator (possible memory corruption)

I've fixed the problem in SWIG, see swig/swig#281 (not merged yet).
The bug has potential to cause memory corruption.
Noticed when trying to add an interface for `mkdtemp`, `uv_fs_s`
layout is totally wrong.

SWIG CFFI binding generator doesn't seem to be particularly
good one, perhaps other options like cffi-grovel (?) may
be considered.