2006-04-25  Murray Cumming  <murrayc@murrayc.com>

        * configure.in:
        * glib/glibmmconfig.h.in:
        * scripts/reduced.m4: Added a --enable-api-default-signal-handlers option. This defines
        GLIBMM_DEFAULT_SIGNAL_HANDLERS_ENABLED, which is used to #ifdef default signal handlers.
        This saves on library code size (less code and API symbols) and application code size and
        loading time (less virtual methods, which must be imported and resolved at load time) and
        per-object memory size (smaller object sizes because of less virtual methods.)
        * tools/m4/class_interface.m4:
        * tools/m4/class_shared.m4: Put default signal handler code in #ifdefs.