Removing "static" from some local variables. This was not thread-safe, code could be not re-entrant.
Note that those "static" was added in the past for some reasons, one was because of speed increase when avoiding allocation/deallocation of data on heap where a temp ChMatrix was needed , but now it is not needed anymore thanks to ChMatrix33 and ChMatrixNM that allocate on stack, and thread safety is a must-have anyway.
Merge branch 'develop' of https://github.com/projectchrono/chrono into develop