This function works like g_param_spec_set_qdata(), but in addition,
a void (*destroy) (gpointer) function may be
specified which is called with @data as argument when the @pspec is
finalized, or the data is being overwritten by a call to
g_param_spec_set_qdata() with the same @quark.
This function works like g_param_spec_set_qdata(), but in addition, a void (*destroy) (gpointer) function may be specified which is called with @data as argument when the @pspec is finalized, or the data is being overwritten by a call to g_param_spec_set_qdata() with the same @quark.