Don't use <sstream> in Streams.h but <iosfwd> instead.

llvm-svn: 32340
diff --git a/llvm/lib/Support/Statistic.cpp b/llvm/lib/Support/Statistic.cpp
index 8c08271..1b28eed 100644
--- a/llvm/lib/Support/Statistic.cpp
+++ b/llvm/lib/Support/Statistic.cpp
@@ -26,6 +26,7 @@
 #include "llvm/Support/Streams.h"
 #include "llvm/ADT/StringExtras.h"
 #include <algorithm>
+#include <ostream>
 using namespace llvm;
 
 // GetLibSupportInfoOutputFile - Return a file stream to print our output on...