swift: Support watch API

Implements Database.watch, and adds an optional timeout variant of
Stream.next to prevent blocking forever (in the case of a watch
that never recieves an event).

The unit tests are not passing for the onChange event -- something
seems to be broken in Go currently.

Change-Id: I6ab82a54605c5259eaec6fdd77e124e16fcbcb7e
diff --git a/services/syncbase/bridge/cgo/lib.h b/services/syncbase/bridge/cgo/lib.h
index fc8565a..64d849a 100644
--- a/services/syncbase/bridge/cgo/lib.h
+++ b/services/syncbase/bridge/cgo/lib.h
@@ -82,9 +82,10 @@
   int n;
 } v23_syncbase_CollectionRowPatterns;
 
+// syncbase.ChangeType
 typedef enum v23_syncbase_ChangeType {
-  kPut = 0,
-  kDelete = 1
+  v23_syncbase_ChangeTypePut = 0,
+  v23_syncbase_ChangeTypeDelete = 1
 } v23_syncbase_ChangeType;
 
 // syncbase.WatchChange