Fixed dbus-c++ gcc 4.7 building problem.

Just add "unistd.h" inclusion to eventloop-integration.h.

BUG=None
TEST=Manually built using gcc 4.7.

Change-Id: I87bd1f90db6a4c974a5ed8134044e8be2034aff2
Reviewed-on: https://gerrit.chromium.org/gerrit/24260
Tested-by: Han Shen <[email protected]>
Reviewed-by: Yunlian Jiang <[email protected]>
Commit-Ready: Han Shen <[email protected]>
diff --git a/include/dbus-c++/eventloop-integration.h b/include/dbus-c++/eventloop-integration.h
index 5108340..1b56ab5 100644
--- a/include/dbus-c++/eventloop-integration.h
+++ b/include/dbus-c++/eventloop-integration.h
@@ -27,6 +27,7 @@
 
 #include <cstring>
 #include <errno.h>
+#include <unistd.h>
 #include "api.h"
 #include "dispatcher.h"
 #include "util.h"