merge revision(s) 44687,44706,44727: [Backport #8770]

	* process.c (recv_child_error): Fix deadlock in rb_fork_internal when a
  signal is sent to the parent process while Ruby is forking in IO.popen.

  Patch by Scott Francis. Closes GH-513.
	* process.c (send_child_error): retry write on EINTR to fix
	  occasional Errno::EINTR from Process.spawn.

	* process.c (recv_child_error): retry read on EINTR to fix
	  occasional Errno::EINTR from Process.spawn.

	* process.c (READ_FROM_CHILD): Apply the last hunk of
	  0001-process.c-avoid-EINTR-from-Process.spawn.patch written by
	  Eric Wong in [Bug #8770].


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_1@45061 b2dd03c8-39d4-4d8f-98ff-823fe69b080e