fix various warnings on Windows

[dirk-thomas]

See http://ci.ros2.org/job/ci_windows/1395/warnings34Result/fixed/

See related changes ros2/rmw_fastrtps#34

@richiprosima FYI

[richiprosima]

Hi @dirk-thomas

I will close your PR for several reasons:

• Your commit @15daf480a7 solves a problem generated by an old version of
  Boost. But with the last one version these changes are not necessary.
• Your commit @96201d1e52 is deprecated because in new release 1.2.0
  AsyncWriterThread was refactored to support more functionality.
• Your commit @578e91a79 was added by us in commit @578e91a79 before the change to Apache License
  2.0. Sorry for the inconveniences.

Thanks for your contributions.