Add testAsync to ThriftTest.thrift which verifies async void works properly.

Summary:
  - testAsync takes a number of seconds to sleep. The test client makes sure
    that the RPC returns in less than 0.2 seconds even though it asks the server
    to sleep for 3 seconds.
  - Implemented this test for C++ and Java.

Test Plan:
  - ran cpp TestServer and TestClient and verified functionality
  - tested cpp and java test server/client against each other - tests passed


git-svn-id: https://svn.apache.org/repos/asf/incubator/thrift/trunk@665484 13f79535-47bb-0310-9956-ffa450edef68
diff --git a/test/cpp/src/TestServer.cpp b/test/cpp/src/TestServer.cpp
index 773225e..14a8a8e 100644
--- a/test/cpp/src/TestServer.cpp
+++ b/test/cpp/src/TestServer.cpp
@@ -255,6 +255,12 @@
       return;
     }
   }
+
+  void testAsync(int sleepFor) {
+    printf("testAsync(%d): Sleeping...\n", sleepFor);
+    sleep(sleepFor);
+    printf("testAsync(%d): done sleeping!\n", sleepFor);
+  }
 };
 
 int main(int argc, char **argv) {