Make ~Operator() protected so subclasses can inherit it and not have

a bunch of errors for all the Operator subclasses such as:

include/llvm/Operator.h:76:7: error: deleted function 'virtual llvm::OverflowingBinaryOperator::~OverflowingBinaryOperator()'
include/llvm/Operator.h:43:3: error: overriding non-deleted function 'virtual llvm::Operator::~Operator()'
include/llvm/Operator.h:76:7: error: 'virtual llvm::OverflowingBinaryOperator::~OverflowingBinaryOperator()' is implicitly deleted because the default definition would be ill-formed:
include/llvm/Operator.h:43:3: error: 'virtual llvm::Operator::~Operator()' is private
include/llvm/Operator.h:76:7: error: within this context

llvm-svn: 166611