Adding initial Teensy 3 support, compiles, but not fully functional yet.

- CDC Output seems to be working
- USB Keyboard output has not been tested, but is "ready"
- UART and Timers have not been tested, or fully utilized
- Issues using Timer 0
- Initial template for MBC-55X Scan module (only module currently compatible with the arm build)
- Updated the interface to the AVR usb module for symmetry with the ARM usb module
- Much gutting was done to the Teensy 3 usb keyboard module, though not in an ideal state yet

Lib/delay.c

@@ -0,0 +1,37 @@
+
+#include "delay.h"
+#include "mk20dx128.h"
+
+// the systick interrupt is supposed to increment this at 1 kHz rate
+volatile uint32_t systick_millis_count = 0;
+
+void yield(void) {};
+
+uint32_t micros(void)
+{
+	uint32_t count, current, istatus;
+
+	__disable_irq();
+	current = SYST_CVR;
+	count = systick_millis_count;
+	istatus = SCB_ICSR; // bit 26 indicates if systick exception pending
+	__enable_irq();
+	if ((istatus & SCB_ICSR_PENDSTSET) && current > ((F_CPU / 1000) - 50)) count++;
+	current = ((F_CPU / 1000) - 1) - current;
+	return count * 1000 + current / (F_CPU / 1000000);
+}
+
+void delay(uint32_t ms)
+{
+	uint32_t start = micros();
+
+	while (1) {
+		if ((micros() - start) >= 1000) {
+			ms--;
+			if (ms == 0) break;
+			start += 1000;
+		}
+		yield();
+	}
+}
+