Release 6.4

    lib(ALL): (( for multiline comments. Comments end with )). Uses recognizers for that from rec-double-paren.frt.
    lib(AVR8): Implement I2C Slave. Renamed i2c.>n to i2c.n@ and i2c.n> to i2c.n!. I2C Generic
    lib(ALL): Recognizer for the Forth 2012 'c' Syntax to replace char c and [char] c. Just load the rec-char.frt file.
    core(AVR8): add >rx-buf (c -- ) that appends a character to the interrupt driven usart ring buffer.