Add two test cases to exercise many expression commands:

    o test_many_expr_commands()
    o test_expr_commands_can_handle_quotes()

Mark test_expr_commands_can_handle_quotes()
as @expectedFailure:

    # rdar://problem/8686536
    # CommandInterpreter::HandleCommand is stripping \'s from input for WantsRawCommand commands

llvm-svn: 121019