tools: rename nfd::tools::nfdc::OutputFormat to ReportFormat

refs #3749

Change-Id: I4984d056c26f9ecbda25103ad60dc50bb60a4dec
diff --git a/tools/nfdc/status-report.hpp b/tools/nfdc/status-report.hpp
index dea9b9f..cfb31f4 100644
--- a/tools/nfdc/status-report.hpp
+++ b/tools/nfdc/status-report.hpp
@@ -36,6 +36,17 @@
 using ndn::security::KeyChain;
 using ndn::Validator;
 
+enum class ReportFormat {
+  XML = 1,
+  TEXT = 2
+};
+
+ReportFormat
+parseReportFormat(const std::string& s);
+
+std::ostream&
+operator<<(std::ostream& os, ReportFormat fmt);
+
 /** \brief collects and prints NFD status report
  */
 class StatusReport : noncopyable