versioner: purge iostreams.

Change-Id: I1b16a4b5c4a8a1333f05636c8c67890d8ce1a090
diff --git a/tools/versioner/src/versioner.cpp b/tools/versioner/src/versioner.cpp
index 3ae0a7b..1b17109 100644
--- a/tools/versioner/src/versioner.cpp
+++ b/tools/versioner/src/versioner.cpp
@@ -289,13 +289,13 @@
     DeclarationAvailability availability;
     if (!decl->calculateAvailability(&availability)) {
       fprintf(stderr, "versioner: failed to calculate availability for declaration:\n");
-      decl->dump(cwd, std::cout, 2);
+      decl->dump(cwd, stderr, 2);
       return false;
     }
 
     if (decl->is_definition && !availability.empty()) {
       fprintf(stderr, "versioner: inline definition has non-empty versioning information:\n");
-      decl->dump(cwd, std::cout, 2);
+      decl->dump(cwd, stderr, 2);
       return false;
     }
   }