Don't do this in practice

This is too complicated and not suitable for event driven server.  We
plan to expose io_service instead.

Merge branch 'pthread-getspecific' of https://github.com/icing/nghttp2 into icing-pthread-getspecific

Fixes GH-170

Fixes GH-172

declaration of make_socket_closeonexec need the proper scope here, it was there per request at https://github.com/tatsuhiro-t/nghttp2/pull/142 , not sure why is was removed.

This reverts commit ef090d42.