Due to website configuration changes, every url starting with http://arduino.cc has been changed to http://www.arduino.cc. Fixes #3191

Author: Federico Fissore

hardware/arduino/avr/libraries/SPI/library.properties

@@ -4,6 +4,6 @@ author=Arduino
 maintainer=Arduino <[email protected]>
 sentence=Enables the communication with devices that use the Serial Peripheral Interface (SPI) Bus. For all Arduino boards, BUT Arduino DUE. 
 paragraph=
-url=http://arduino.cc/en/Reference/SPI
+url=http://www.arduino.cc/en/Reference/SPI
 architectures=avr