Merge pull request #371 from Banjer/Melzi_LED_PIN

Chenged LED_PIN for Melzi boards, added comment about broken versions of...

Marlin/Marlin_main.cpp

@@ -88,7 +88,7 @@
 // M29  - Stop SD write
 // M30  - Delete file from SD (M30 filename.g)
 // M31  - Output time since last M109 or SD card start to serial
-// M42  - Change pin status via gcode
+// M42  - Change pin status via gcode Use M42 Px Sy to set pin x to value y, when omitting Px the onboard led will be used.
 // M80  - Turn on Power Supply
 // M81  - Turn off Power Supply
 // M82  - Set E codes absolute (default)

Marlin/pins.h

@@ -683,7 +683,7 @@
 #endif
 
 #ifdef MELZI
-#define LED_PIN            28
+#define LED_PIN            27 /* On some broken versions of the Sanguino libraries the pin definitions are wrong, which then needs LED_PIN as pin 28. But you better upgrade your Sanguino libraries! See #368. */
 #define FAN_PIN            4
 #endif