"library_setup()" in this case is probably "xsample_setup();" 
EDIT: Looks like it might be "xsample_main()" judging from the main.cpp, although the usual pd external conventions noted in the readme is LIBRARYNAME_setup(). In this case, xsample is using Flext which abstracts writing dsp externals between pd and max so I imagine "xsample_setup()" is probably declared via Flext for compatibility with pd.
