Merge pull request #193 from Snafu/patch-1

Fixed UART 3 check (oops - cut&pasteO)

optiboot/bootloaders/optiboot/pin_defs.h

@@ -61,7 +61,7 @@
 # define UART_SRL UBRR2L
 # define UART_UDR UDR2
 #elif UART == 3
-#if !defined(UDR1)
+#if !defined(UDR3)
 #error UART == 3, but no UART3 on device
 #endif
 # define UART_SRA UCSR3A