Added comment for OUTPUT_PULLUP

Author: totalretribution

src/Adafruit_MCP23X18.h

@@ -7,7 +7,7 @@
 
 #include "Adafruit_MCP23X17.h"
 
-#define OUTPUT_PULLUP 4
+#define OUTPUT_PULLUP 4 //!< Additional define for Output with Pullup
 
 /**************************************************************************/
 /*!
@@ -22,4 +22,4 @@ class Adafruit_MCP23X18 : public Adafruit_MCP23X17 {
 
 };
 
-#endif
+#endif