Manchester Library Won't Compile for Attiny85
attiny is missing an option required to allow the Manchester library to function properly on ATtinyX5 devices, specifically definition of __AVR_ATtinyX5__ when a device is selected. In fact, it's missing quite a few things. 

The package I use for ATtinyX5 support is arduino-tiny. I have verified that it defines that symbol properly. I recommend that you dump your current support package and install arduino-tiny instead.