Fix PORT-146: Have told all C++ builds on the Mac to use libstdc++ now.
XCode on Mavericks started defaulting to libc++ so that was causing the
problems. Can now happily build and run the unit tests for HLA v1.3 from
the command line, as well as build in Eclipse.
Merge pull request #38 from openlvc/port146-cpp-tests-macosx

PORT-146: Fix unit tests and HLA v1.3 build on Mac OS X Mavericks