Make the Mass Storage bootloader compatible with the original (green) XPLAIN boards.

Bootloaders/MassStorage/BootloaderMassStorage.c

@@ -73,6 +73,21 @@ void Application_Jump_Check(void)
 		PORTC &= ~(1 << 7);
 	#endif
 
+	#if ((BOARD == BOARD_XPLAIN) || (BOARD == BOARD_XPLAIN_REV1))
+		/* Disable JTAG debugging */
+		JTAG_DISABLE();
+
+		/* Enable pull-up on the JTAG TCK pin so we can use it to select the mode */
+		PORTF |= (1 << 4);
+		Delay_MS(10);
+
+		/* If the TCK pin is not jumpered to ground, start the user application instead */
+		JumpToApplication |= ((PINF & (1 << 4)) != 0);
+
+		/* Re-enable JTAG debugging */
+		JTAG_ENABLE();
+	#endif
+
 	if (JumpToApplication)
 	{
 		// cppcheck-suppress constStatement