fix '-0 === 0 => true'
add EJS_INSTALL_ATOM_FUNCTION_LEN_FLAGS macro that we can use instead of EJS_INSTALL_ATOM_FUNCTION_FLAGS when populating prototype/object methods in order to specify the value of the length property.  use that in the places where its lack is causing test262 failures.  we need to make a pass over the spec and decorate all builtin methods with proper length values.  also fix some Math.hypot/Math.clz edge case behavior.