Include <cassert> in main.cc.

We are doing an assert in main, but the assert header is being pulled in
by an include that is about to go.  Make it explicit.


git-svn-id: https://svn.apache.org/repos/asf/incubator/thrift/trunk@665587 13f79535-47bb-0310-9956-ffa450edef68
diff --git a/compiler/cpp/src/main.cc b/compiler/cpp/src/main.cc
index e44c9b3..6b80ff5 100644
--- a/compiler/cpp/src/main.cc
+++ b/compiler/cpp/src/main.cc
@@ -15,6 +15,7 @@
  * @author Mark Slee <mcslee@facebook.com>
  */
 
+#include <cassert>
 #include <stdlib.h>
 #include <stdio.h>
 #include <stdarg.h>