Fix leak in BasicCalleeAnalysis.

Each time we delete the pass manager, we delete the analyses it
holds. In this analysis we were holding onto memory that wasn't getting
released when the analysis was deleted.

Fixes rdar://problem/26245872.

Author: rudkx

include/swift/SILOptimizer/Analysis/BasicCalleeAnalysis.h

@@ -118,7 +118,7 @@ class CalleeCache {
 
 class BasicCalleeAnalysis : public SILAnalysis {
   SILModule &M;
-  CalleeCache *Cache;
+  std::unique_ptr<CalleeCache> Cache;
 
 public:
   BasicCalleeAnalysis(SILModule *M)
@@ -129,17 +129,15 @@ class BasicCalleeAnalysis : public SILAnalysis {
   }
 
   virtual void invalidate(SILAnalysis::InvalidationKind K) {
-    if (K & InvalidationKind::Functions) {
-      delete Cache;
-      Cache = nullptr;
-    }
+    if (K & InvalidationKind::Functions)
+      Cache.reset();
   }
 
   virtual void invalidate(SILFunction *F, InvalidationKind K) { invalidate(K); }
 
   CalleeList getCalleeList(FullApplySite FAS) {
     if (!Cache)
-      Cache = new CalleeCache(M);
+      Cache = llvm::make_unique<CalleeCache>(M);
 
     return Cache->getCalleeList(FAS);
   }