Allow propagators to access solving actions in decide callback

This allows propagators to branch on new literals that the propagator
might (later) assign its own meaning to.

crates/pindakaas/src/solver.rs

@@ -173,7 +173,8 @@ pub trait Propagator {
 
 	/// Method called when the solver asks for the next decision literal. If it
 	/// returns None, the solver makes its own choice.
-	fn decide(&mut self) -> Option<Lit> {
+	fn decide(&mut self, slv: &mut dyn SolvingActions) -> Option<Lit> {
+		let _ = slv;
 		None
 	}
 

crates/pindakaas/src/solver/libloading.rs

@@ -492,9 +492,12 @@ pub(crate) unsafe extern "C" fn ipasir_check_model_cb<P: Propagator, A: SolvingA
 	prop.prop.check_model(&mut prop.slv, &value)
 }
 #[cfg(feature = "ipasir-up")]
-pub(crate) unsafe extern "C" fn ipasir_decide_cb<P: Propagator, A>(state: *mut c_void) -> i32 {
+pub(crate) unsafe extern "C" fn ipasir_decide_cb<P: Propagator, A: SolvingActions>(
+	state: *mut c_void,
+) -> i32 {
 	let prop = &mut *(state as *mut IpasirPropStore<P, A>);
-	if let Some(l) = prop.prop.decide() {
+	let slv = &mut prop.slv;
+	if let Some(l) = prop.prop.decide(slv) {
 		l.0.into()
 	} else {
 		0