[issue27945] Various segfaults with dict

[INADA Naoki]

INADA Naoki added the comment:

0001-Issue-27945-fix-dictiter_iternextitem-use-after-free.patch	LGTM and OK too.
But 0001-Issue-27945-Fixed-segfaults-in-dict.fromkeys-when-it.patch	cause conflict.

I want to commit first three patches.
For another reviewer, here is the patch merging three patches. Please review it.

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Added file: http://bugs.python.org/file45500/27945-dict-segv-py27.patch

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<http://bugs.python.org/issue27945>
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