Rework and fix the implementation of MinMeanCycle (#179)

- Fix the handling of the cycle means.
- Many implementation improvements:
- More efficient data storage for the strongly connected
components.
- Better handling of BFS queues.
- Merge consecutive BFS searches (perform two BFS searches
instead of three).

This version is about two times faster on average and an order of
magnitude faster if there are a lot of strongly connected components.

SET(LEMON_INCLUDE_DIR "@CMAKE_INSTALL_PREFIX@/include" CACHE PATH "LEMON include directory")

SET(LEMON_INCLUDE_DIRS "${LEMON_INCLUDE_DIR}")

IF(UNIX)

  SET(LEMON_LIB_NAME "libemon.a")

ELSEIF(WIN32)

  SET(LEMON_LIB_NAME "lemon.lib")

ENDIF(UNIX)

SET(LEMON_LIBRARY "@CMAKE_INSTALL_PREFIX@/lib/${LEMON_LIB_NAME}" CACHE FILEPATH "LEMON library")

SET(LEMON_LIBRARIES "${LEMON_LIBRARY}")

MARK_AS_ADVANCED(LEMON_LIBRARY LEMON_INCLUDE_DIR)