futures/Barrier.cpp uses DCHECK which implies a glog dependency

Summary:
When compiling each file individually, bring the includes
closer as they are referenced (e.g., rely less on transitive includes
and include what you use)

Reviewed By: bithree

Differential Revision: D18864197

fbshipit-source-id: 24adef418fd2eb944aa283a55411ec5a7c6f549b

folly/futures/Barrier.cpp

@@ -17,6 +17,8 @@
 #include <folly/futures/Barrier.h>
 #include <folly/lang/Exception.h>
 
+#include <glog/logging.h>
+
 namespace folly {
 namespace futures {