tree c0c230df3f080cf54602d1e2040248a06d01e525
parent d570d48648503e57f3abfcd9b9516583768fec48
author Thomas Van Lenten <thomasvl@google.com> 1517432250 -0500
committer Thomas Van Lenten <thomasvl@google.com> 1517435873 -0500

Work around strange error with atomic and swift under Xcode 8.3.3.

Haven't been able to make a repo case, but this should "fix" the problem
by avoid it completely.

- Move readOnlySemaphore_ into the .m file so it isn't exposed in any
  header.
- Move GPBGetObjectIvarWithField() also to go with the new limited
  visibility on the readOnlySemaphore_.