2.99.4 (unstable): * Minor documentation improvements. (Murray Cumming) * Make some constructors explicit. (Murray Cumming) * Some more minor uses of C++11 syntax. (Murray Cumming) * Remove unused SIGC_FUNCTORS_DEDUCE_RESULT_TYPE_WITH_DECLTYPE. (Murray Cumming) * Reformat code with clang-format. (Murray Cumming)