new_valist
Description:
Creates a new signal.
(This is usually done in the class initializer.)
See @new for details on allowed signal names.
If c_marshaller is null, g_cclosure_marshal_generic will be used as the marshaller for this 
      signal.
Parameters:
| signal_name | the name for the signal | 
| itype | the type this signal pertains to. It will also pertain to types which are derived from this type. | 
| signal_flags | a combination of SignalFlags specifying detail of when the default handler is to be invoked. You should at least specify g_signal_run_first or g_signal_run_last. | 
| class_closure | The closure to invoke on signal emission; may be null. | 
| accumulator | the accumulator for this signal; may be null. | 
| c_marshaller | the function to translate arrays of parameter values to signal emissions into C language callback invocations or null. | 
| return_type | the type of return value, or g_type_none for a signal without a return value. | 
| n_params | the number of parameter types in  | 
| args | va_list of Type, one for each parameter. | 
| accu_data | user data for the  | 
Returns:
| the signal id |