As of commit 2e81e8a, the option to set the C++ language standard that was previously located in the build configuration settings of some exporters has now moved to the main project settings and is set to C++11 by default. This means that projects that had a specific verison of the C++ language standard set for exporter build configurations will instead use the default (C++11) when re-saving with the new Projucer. You can change this to C++14 or the latest (C++1z) by modifying the option in the project settings, located here:
This will hopefully make it easier to change the C++ language standard for a whole project and have that setting propagate to all exporters.