Visual Studio default toolset uses 32bit executables for compiling which
means that if it uses more than 4GB of memory per instance it crashes.
By moving the ConnectivityTracer into a separate compilation unit we
can help out the compiler.
This also improved compilation times and library size:
Old:
build time (j8): 48.62 real
lib size: 6.2MB
New:
build time (j8): 41.31 real
lib size: 5.0MB
