bumping library for compilation on m4 targets (#151)

Author: brentru

Adafruit_MQTT.cpp

@@ -21,7 +21,7 @@
 // SOFTWARE.
 #include "Adafruit_MQTT.h"
 
-#if defined(ARDUINO_SAMD_ZERO) || defined(ARDUINO_SAMD_MKR1000)
+#if defined(ARDUINO_SAMD_ZERO) || defined(ARDUINO_SAMD_MKR1000) || defined(ARDUINO_ARCH_SAMD)
 static char *dtostrf (double val, signed char width, unsigned char prec, char *sout) {
   char fmt[20];
   sprintf(fmt, "%%%d.%df", width, prec);