UART error can not compile on Arduino Yun (ATmega32u4)
Those register names are for a different chip (maybe the ATMega328P of the Uno).

Instead you need to use the right register names.  Start by reading the datasheet for the ATMega32U4.  You might find that the register names are UCSR1A etc, or UCSRA or something like that instead of UCSR0A.