Make conditions explicit in races

And boot recursive spending plans. That path required heap allocations.
Since we don't have a need for this generality right now, reduce the
language to the smallest one that can pass our test suite.

src/accountant.rs

@@ -5,7 +5,7 @@
 use hash::Hash;
 use entry::Entry;
 use event::Event;
-use plan::{Action, Plan};
+use plan::{Action, Plan, PlanEvent};
 use transaction::Transaction;
 use signature::{KeyPair, PublicKey, Signature};
 use mint::Mint;
@@ -141,7 +141,7 @@ impl Accountant {
         }
 
         let mut plan = tr.plan.clone();
-        let actionable = plan.process_verified_timestamp(self.last_time);
+        let actionable = plan.process_event(PlanEvent::Timestamp(self.last_time));
 
         if !actionable {
             self.pending.insert(tr.sig, plan);
@@ -154,7 +154,7 @@ impl Accountant {
 
     fn process_verified_sig(&mut self, from: PublicKey, tx_sig: Signature) -> Result<()> {
         let actionable = if let Some(plan) = self.pending.get_mut(&tx_sig) {
-            plan.process_verified_sig(from)
+            plan.process_event(PlanEvent::Signature(from))
         } else {
             false
         };
@@ -186,7 +186,7 @@ impl Accountant {
         // Check to see if any timelocked transactions can be completed.
         let mut completed = vec![];
         for (key, plan) in &mut self.pending {
-            if plan.process_verified_timestamp(self.last_time) {
+            if plan.process_event(PlanEvent::Timestamp(self.last_time)) {
                 completed.push(key.clone());
             }
         }