Add StructuredData plugin type; showcase with new DarwinLog feature

Take 2, with missing cmake line fixed.  Build tested on
Ubuntu 14.04 with clang-3.6.

See docs/structured_data/StructuredDataPlugins.md for details.

differential review: https://reviews.llvm.org/D22976

reviewers: clayborg, jingham
llvm-svn: 279202
diff --git a/lldb/tools/debugserver/source/MacOSX/DarwinLog/DarwinLogEvent.h b/lldb/tools/debugserver/source/MacOSX/DarwinLog/DarwinLogEvent.h
new file mode 100644
index 0000000..6be3b81
--- /dev/null
+++ b/lldb/tools/debugserver/source/MacOSX/DarwinLog/DarwinLogEvent.h
@@ -0,0 +1,27 @@
+//===-- DarwinLogEvent.h ----------------------------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef DarwinLogEvent_h
+#define DarwinLogEvent_h
+
+#include <memory>
+#include <vector>
+
+#include "JSONGenerator.h"
+
+// =============================================================================
+/// Each discrete unit of information is described as an event, such as
+/// the emission of a single log message.
+// =============================================================================
+
+using DarwinLogEvent = JSONGenerator::Dictionary;
+using DarwinLogEventSP = std::shared_ptr<DarwinLogEvent>;
+using DarwinLogEventVector = std::vector<DarwinLogEventSP>;
+
+#endif