update comment, secure_allocator is defined in allocators.h

src/key.h

@@ -99,7 +99,7 @@ public:
 };
 
 
-// secure_allocator is defined in serialize.h
+// secure_allocator is defined in allocators.h
 // CPrivKey is a serialized private key, with all parameters included (279 bytes)
 typedef std::vector<unsigned char, secure_allocator<unsigned char> > CPrivKey;
 // CSecret is a serialization of just the secret parameter (32 bytes)