Go: improved support for literal numbers, add unicode escape characters and new predefined type
- add binary (0b) and octal (0o) prefix
- add hedecimal float format (0x1.fp-2)
- add imaginary suffix (123i)
- add digit separator (1_2_3)
- add any and comparable keyword type
- add little Unicode escapes ('\uHHHH') and big Unicode escapes ('\uHHHHHHHH')