Fix PaX

[forgottenswitch]

Drop ClosurePool in favor of PaX-compatible libffi functions.

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4845 examples, 0 failures

[forgottenswitch]

Verified with

gem uninstall ffi
gem build ffi.gemspec
gem install ./ffi-1.9.14.gem
cd
jekyll new hello_jekyll
cd hello_jekyll
bundle exec jekyll serve
# It works on http://localhost:4000

[forgottenswitch]

Oops, fails on MacOS

[forgottenswitch]

It doesn't rake test with stable libffi 3.2.1, but does with latest master.
Perhaps there should be a 3.2.2 release then?

[tduehr]

Thanks, I'll look at this and incorporate some of your changes into the libffi update branch and we'll see what's left after that.

[tduehr]

Can you rebase off the current master? Some of this may have been addressed from the ppc64le fixes.

[forgottenswitch]

Done.

Feel free to ignore this [and merge anyway], but PaX itself could be patched instead, as being overly-restrictive. Current (incomplete, but sufficient for the case) state:

• PaX patch series
• userspace support