Renamings in connectivity.h and bug fix in DfsVisit (#61)

- The include guard, the private namespace and some local varibles
are renamed
- The stop() must be called in DfsVisit, if there are not outgoing
arcs from the added node

if WANT_TOOLS

bin_PROGRAMS += \

	tools/dimacs-to-lgf

dist_bin_SCRIPTS += tools/lemon-0.x-to-1.x.sh

endif WANT_TOOLS

tools_dimacs_to_lgf_SOURCES = tools/dimacs-to-lgf.cc