Implement built-in help.
Implement built-in help.

This requires copying __doc__ and for good measure __name__, in the
_nullary, _unary, and _binary wrappers because you can't
inspect.signature on many math functions, etc. Too bad we can't
functools.wraps here.

Unfortunately, it relies on builtins help, so there's some confusing
extra crap in the output. Whatever.

pilona/RPN,pilona/RPN