General improvements in weighted matching algorithms (#314)

- Fix include guard
- Uniform handling of MATCHED and UNMATCHED blossoms
- Prefer operations which decrease the number of trees
- Fix improper use of '/='

The solved problems did not cause wrong solution.

#define LEMON_VERSION "@PROJECT_VERSION@"

#cmakedefine LEMON_HAVE_LONG_LONG 1

#cmakedefine LEMON_HAVE_LP 1

#cmakedefine LEMON_HAVE_MIP 1

#cmakedefine LEMON_HAVE_GLPK 1

#cmakedefine LEMON_HAVE_CPLEX 1

#cmakedefine LEMON_HAVE_CLP 1

#cmakedefine LEMON_HAVE_CBC 1