Add improvements to the python3 syntax definitions (#1833)

Add improvements to the python3 syntax definitions (#1833)

* Python3: Add built-in object 'cls'

* Python3: Add the bitwise negation operator ~

* Python3: Add support for hexadeximal and binary numerical literals

* Python3: Rewrite '(__foo__|__bar__)' as '__(foo|bar)__', add known '__i.*__' methods

* Python3: Add __iter__ as a magic method, sort the list of magic methods

* Python3: Numerical literals: Add support for '_', disallow leading 0 for decimals

* fixup! Python3: Numerical literals: Add support for '_', disallow leading 0 for decimals

hex oct and bin have different sets of allowed digits

* Python3: Add support for floating point numbers with optional scientific notation

* Python3: stop single-line strings at EOL

* Python3: Add support for TODO and FIXME in comments

* Python3: Add support for the ^ bitwise xor operator