fails:String#lstrip returns a copy of self with leading whitespace removed
fails:String#lstrip does not strip leading  
fails:String#lstrip taints the result when self is tainted
fails:String#lstrip! modifies self in place and returns self
fails:String#lstrip! returns nil if no modifications were made
fails:String#lstrip! raises a RuntimeError on a frozen instance that is modified
fails:String#lstrip! raises a RuntimeError on a frozen instance that would not be modified
