Remove CMSIS + gcc7 warnings

Author: facchinm

cores/arduino/Print.cpp

@@ -16,9 +16,6 @@
   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 */
 
-#include <stdlib.h>
-#include <stdio.h>
-#include <string.h>
 #include <math.h>
 #include "Arduino.h"
 

cores/arduino/USB/USBCore.cpp

@@ -774,6 +774,7 @@ bool USBDeviceClass::handleStandardSetup(USBSetup &setup)
 			sendZlp(0);
 			return true;
 		}
+		break;
 
 	case SET_ADDRESS:
 		setAddress(setup.wValueL);
@@ -813,6 +814,7 @@ bool USBDeviceClass::handleStandardSetup(USBSetup &setup)
 	default:
 		return true;
 	}
+	return true;
 }
 
 void USBDeviceClass::ISRHandler()

cores/arduino/USB/samd21_host.c

@@ -16,17 +16,9 @@
   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 */
 
-
-#include <stdio.h>
-#include <stdint.h>
-#include <string.h>
-
-#include "../Arduino.h"
-#include "variant.h"
+#include "Arduino.h"
 #include "USB_host.h"
 #include "samd21_host.h"
-#include "sam.h"
-#include "wiring_digital.h"
 #include "wiring_private.h"
 
 #define HOST_DEFINED

cores/arduino/Uart.cpp

@@ -16,9 +16,9 @@
   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 */
 
-#include "Uart.h"
 #include "Arduino.h"
 #include "wiring_private.h"
+#include "Uart.h"
 
 #define NO_RTS_PIN 255
 #define NO_CTS_PIN 255