Making all iterators exposed from exception_list const
Unify and simplify handling of exceptions. Adding missing header file for parallel::exception_list.
Replace '>>' with '> >'
Fixing is_parallel_execution_policy to be false by default
Marking handle_exception() as BOOST_ATTRIBUTE_NORETURN
Removing static_asserts which are not needed, adding additional assert.
Adding static assert to make sure algorithm_result is not invoked with a lvalue reference.