[NaCl SDK] Add nacl_io and sdk_util namespaces.

native_client_sdk/src/libraries/sdk_util/thread_pool.cc

Index: native_client_sdk/src/libraries/sdk_util/thread_pool.cc
diff --git a/native_client_sdk/src/libraries/sdk_util/thread_pool.cc b/native_client_sdk/src/libraries/sdk_util/thread_pool.cc
index e2b794372f0602a6be0479bb24c72ca45bfacc92..1d4e2cb3f7ab56ab0d9286e0ca2944f940460f24 100644
--- a/native_client_sdk/src/libraries/sdk_util/thread_pool.cc
+++ b/native_client_sdk/src/libraries/sdk_util/thread_pool.cc
@@ -11,6 +11,8 @@
 
 #include "sdk_util/auto_lock.h"
 
+namespace sdk_util {
+
 // Initializes mutex, semaphores and a pool of threads.  If 0 is passed for
 // num_threads, all work will be performed on the dispatch thread.
 ThreadPool::ThreadPool(int num_threads)
@@ -134,3 +136,5 @@ void ThreadPool::Dispatch(int num_tasks, WorkFunction work, void* data) {
     DispatchHere(num_tasks, work, data);
 }
 
+}  // namespace sdk_util
+