THRIFT-214. cpp: Qualify another cast

r722337 only fixed one occurrence of this issue.
Not sure why this one hasn't been a problem before,
but it is breaking compilation on Mac OS 10.6.

git-svn-id: https://svn.apache.org/repos/asf/incubator/thrift/trunk@810150 13f79535-47bb-0310-9956-ffa450edef68
diff --git a/lib/cpp/src/concurrency/PosixThreadFactory.cpp b/lib/cpp/src/concurrency/PosixThreadFactory.cpp
index 893dc80..d42288c 100644
--- a/lib/cpp/src/concurrency/PosixThreadFactory.cpp
+++ b/lib/cpp/src/concurrency/PosixThreadFactory.cpp
@@ -286,8 +286,7 @@
   void setDetached(bool value) { detached_ = value; }
 
   Thread::id_t getCurrentThreadId() const {
-    // TODO(dreiss): Stop using C-style casts.
-    return (id_t)pthread_self();
+    return (Thread::id_t)pthread_self();
   }
 
 };