1.12.0 release notes mention OMSimulator, but this is not part of OpenModelica super-project

[Martin Sjölund]

If we're going to announce including something in OpenModelica (like we did for 1.12.0), this needs to be tested on all platforms and as it is, the source code for OMSimulator is not part of the release tarballs (because there is no submodule for OMSimulator in OpenModelica.git).

For the v1.13.0 we need to have included OMSimulator in the super-project and verified that the installers include the packages (and that OMEdit finds the simulator without setting up paths, etc).

We also need to build and test the simulator on each commit if we include it in OpenModelica (at least each commit that changes the simulator).