Introduce Platform::Log (#1640)

* Add Platform::Log and Platform::LogLevel

* Replace most printf calls with Platform::Log calls

* Move a brace down

* Move some log entries to one Log call

- Some implementations of Log may assume a full line

* Log the MAC address as LogLevel::Info

src/Platform.h

@@ -128,6 +128,16 @@ inline bool LocalFileExists(std::string name)
     return true;
 }
 
+enum LogLevel
+{
+    Debug,
+    Info,
+    Warn,
+    Error,
+};
+
+void Log(LogLevel level, const char* fmt, ...);
+
 struct Thread;
 Thread* Thread_Create(std::function<void()> func);
 void Thread_Free(Thread* thread);