Support of MSL 3.2.3

[Francesco Casella]

The MSL 3.2.3 was ​officially released today.

MSL 3.2.3 has a number of fixes w.r.t. 3.2.2, and a lot more models. The coverage is very high: 408/424 models simulate with the old front-end, and 406/424 with the new one (see also #5288); we are also actively addressing the remaining issues, so I think we should make it the default option in 1.14.0.

We need to carry out the following actions ASAP:

• Add the reference results file, which are found in these two GIT-LFS repos ​https://github.com/modelica/MAP-LIB_ReferenceResults.git, branch v3.2.3
• Check if we still need to patch MSL 3.2.3 to run on OMC (I hope not) and, if so, set up the patch file
• Add Modelica_3.2.3 to the testuite
• Add Modelica_3.2.3 to the shipped libraries

It would also be nice to rename Modelica_trunk to Modelica_master, since we are now on GIT for good, unless this creates problems with history or other things.