Fix undefined function warnings

Firmware/adc.c

@@ -2,7 +2,7 @@
 
 #include "adc.h"
 #include <avr/io.h>
-
+#include <stdio.h>
 
 uint8_t adc_state;
 uint8_t adc_count;

Firmware/sm4.c

@@ -1,6 +1,7 @@
 //sm4.c - simple 4-axis stepper control
 
 #include "sm4.h"
+#include <math.h>
 #include <avr/io.h>
 #include <avr/pgmspace.h>