add "Do nothing" app

src/app/donothing/Makefile.inc

+timer_cycles = 0
+timer_s = 0
+loop = 0

src/app/donothing/main.cc

+#include "arch.h"
+#include "driver/gpio.h"
+#include "driver/stdout.h"
+#include "driver/uptime.h"
+
+int main(void)
+{
+	arch.setup();
+	gpio.setup();
+	kout.setup();
+
+	kout << "Hello, World!" << endl;
+	kout << "Naptime." << endl;
+
+	arch.idle();
+
+	return 0;
+}