[Sync] Put everything in sync/api into csync namespace

sync/api/sync_change.cc

Index: sync/api/sync_change.cc
diff --git a/sync/api/sync_change.cc b/sync/api/sync_change.cc
index 627c19bf51f80de127688c19d875e42450e9e5bc..ef9063b5fc450f908d48e77017d52e184abe716b 100644
--- a/sync/api/sync_change.cc
+++ b/sync/api/sync_change.cc
@@ -6,6 +6,8 @@
 
 #include <ostream>
 
+namespace csync {
+
 SyncChange::SyncChange() : change_type_(ACTION_INVALID) {
 }
 
@@ -71,3 +73,5 @@ std::string SyncChange::ToString() const {
 void PrintTo(const SyncChange& sync_change, std::ostream* os) {
   *os << sync_change.ToString();
 }
+
+}  // namespace csync