ATtiny4313 Hardware Serial RX issue

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What steps will reproduce the problem?
Using an Arduino Uno as a programmer and serial interface (TX and RX pins on 
the UNO connecting directly to TX and RX pins on the ATtiny4313)

1. Setup Serial.begin(9600);
2. In loop() add if(Serial.available()){ Serial.println(Serial.read()); }
3. Send anything to the ATtiny4313 through serial

What is the expected output? What do you see instead?
The output should be the character(s) you entered either in HEX, DEC or char 
format, instead the serial window floods with 0's indefinitely

What version of the product are you using? On what operating system?
Arduino IDE 1.6.3 (Same result in every version) Windows 7 x64

Please provide any additional information below.
I was able to get the RX pin working correctly using the attiny2313_core.zip 
file found here http://hci.rwth-aachen.de/luminet and copying and pasting c++ 
and header files from the actual arduino core folder when error message popped 
up during compile so this leads me to believe there's an issue with the 
Arduino-Tiny core that needs to be resolved.

Original issue reported on code.google.com by [email protected] on 22 May 2015 at 9:05