This commit finishes the removal of OpenMP from the KiCad codebase.
Removed in this commit are the OpenMP calls in 3d-viewer and
qa/polygon_triangulation as well as all references in CMakeLists.txt
std::thread is used instead for multithreaded computation
OpenMP is not available for macos, so moving to a std::threads
implementation brings platforms into shared code.
This also reduces the OpenMP overhead when computing connectivity and
ratsnests.
Fixes: lp:1780130
* https://bugs.launchpad.net/kicad/+bug/1780130
Seth Hillbrand
Simon Richter
jean-pierre charras
Tomasz Włostowski