Add millis() and fix warnings

Author: facchinm

cores/arduino/Arduino.h

@@ -30,7 +30,7 @@ inline void NVIC_SystemReset() {}
 #define Stream MbedStream
 #include "mbed.h"
 #undef PinMode
-#undef String
+#undef Stream
 #endif
 
 #define PinMode ArduinoPinMode

cores/arduino/api

@@ -1 +1 @@
-/home/martino/ArduinoCore-API/api
+/home/martino/Arduino/hardware/arduino-git/ArduinoCore-API/api/

cores/arduino/wiring.cpp

@@ -22,11 +22,13 @@
 
 #include "wiring_private.h"
 
-unsigned long millis()
+inline unsigned long millis()
 {
+  return us_ticker_read() / 1000L;
 }
 
-unsigned long micros() {
+inline unsigned long micros() {
+  return us_ticker_read();
 }
 
 void delay(unsigned long ms)

cores/arduino/wiring_digital.cpp

@@ -39,6 +39,9 @@ void pinMode(uint8_t pin, PinMode mode)
     case INPUT_PULLUP:
       gpio_init_inout(&gpio[pin], (PinName)pin, PIN_INPUT, PullUp, 0);
       break;
+    case INPUT_PULLDOWN:
+      gpio_init_inout(&gpio[pin], (PinName)pin, PIN_INPUT, PullDown, 0);
+      break;
   }
 }