[nfc] Iwyu: forward-declare/include  raw_ostream in zone algo

llvm-svn: 318517
diff --git a/polly/lib/Transform/ZoneAlgo.cpp b/polly/lib/Transform/ZoneAlgo.cpp
index 96bfac4..552dc83 100644
--- a/polly/lib/Transform/ZoneAlgo.cpp
+++ b/polly/lib/Transform/ZoneAlgo.cpp
@@ -154,6 +154,7 @@
 #include "polly/Support/GICHelper.h"
 #include "polly/Support/ISLTools.h"
 #include "polly/Support/VirtualInstruction.h"
+#include "llvm/Support/raw_ostream.h"
 #include "llvm/ADT/Statistic.h"
 
 #define DEBUG_TYPE "polly-zone"