Ok folks, I fixed all the paths in the simulte *.h to use full pathnames. Someone please merge this into simulte. This should make it work for windows, provided you unzip the files into omnetpp/samples.
omnetpp 5.1 removed support for recursive includes in opp_makemake, so simulte wasn't able to find files from inet (and even within simulte), since the makefile did not include those directories anymore.
https://github.com/hchenji/simulte