Using boost prior to 1.40.0 and using Services

If you're using Services, and a boost version < 1.40.0, it's recommended to
upgrade your boost version to 1.40.0 or later when upgrading to the Toolchain
2.3.

We've been having 'bad_weak_ptr' exceptions in constructors of Services. I
have fixed it but did not succeed with 'backporting' the fix to boost versions
before 1.40.

Some revisions on master contain a non-working fix. Make sure you have the
latest HEAD.

Peter