Default CS pins for Ethernet on Teensy 2.0 & Teensy++ 2.0

teensy/pins_arduino.h

 #define NUM_DIGITAL_PINS                CORE_NUM_TOTAL_PINS
 #define NUM_ANALOG_INPUTS               CORE_NUM_ANALOG
 
+// default CS pin to use for Ethernet library
+#if defined(__AVR_ATmega32U4__)
+#define PIN_SPI_SS_ETHERNET_LIB 0
+#elif defined(__AVR_AT90USB646__) || defined(__AVR_AT90USB1286__)
+#define PIN_SPI_SS_ETHERNET_LIB 20
+#endif
 
 // This allows CapSense to work.  Do any libraries
 // depend on these to be zero?