add test/benchmark app for MSP430 EnergyTrace time resolution

src/app/energybench/Makefile.inc

+timer_cycles ?= 1
+loop ?= 1

src/app/energybench/main.cc

+#include "arch.h"
+#include "driver/gpio.h"
+#include "driver/stdout.h"
+#include "driver/uptime.h"
+
+#ifndef TIMER_CYCLES
+#error makeflag timer_cycles=1 required
+#endif
+
+void loop(void)
+{
+#if 0
+	static unsigned char i = 0;
+
+	switch (i) {
+		case 0:
+			gpio.led_on(0);
+			gpio.led_off(0);
+			break;
+		case 1:
+			gpio.led_on(0);
+			arch.delay_us(1);
+			gpio.led_off(0);
+			break;
+		case 2:
+			gpio.led_on(0);
+			arch.delay_us(2);
+			gpio.led_off(0);
+			break;
+		case 3:
+			gpio.led_on(1);
+			gpio.led_off(1);
+			break;
+		case 4:
+			gpio.led_on(1);
+			arch.delay_us(1);
+			gpio.led_off(1);
+			break;
+		case 5:
+			gpio.led_on(1);
+			arch.delay_us(2);
+			gpio.led_off(1);
+			break;
+		case 6:
+			gpio.led_on(0);
+			break;
+		case 7:
+			gpio.led_off(0);
+			break;
+		case 8:
+			gpio.led_on(1);
+			break;
+		case 9:
+			gpio.led_off(1);
+			break;
+		default:
+			break;
+	}
+	
+
+	i = (i+1) % 10;
+#endif
+}
+
+int main(void)
+{
+	arch.setup();
+	gpio.setup();
+	kout.setup();
+
+	kout << "Hello, World!" << endl;
+	kout << "Test, World!" << endl;
+	kout << dec << uptime.get_cycles() << endl;
+	kout << dec << uptime.get_cycles() << endl;
+	kout << dec << uptime.get_cycles() << endl;
+	kout << dec << uptime.get_cycles() << endl;
+
+	arch.idle_loop();
+
+	return 0;
+}