* lib/Automake/Conditional.pm: Add reference to ConditionalSet.pm. * lib/Automake/ConditionalSet.pm: New file. * lib/Automake/Makefile.am (dist_perllib_DATA): Add ConditionalSet.pm. * automake.in: Use ConditionalSet. (by_condition, invert_conditions, variable_conditions_permutations): Remove, now defined as Automake::ConditionalSet::by_condition, Automake::ConditionalSet::invert, and Automake::ConditionalSet::permutations. (variable_sorted_conditions): Remove. (msg_var, msg_target handle_source_transform, handle_lib_objects, conditional_ambiguous_p, variable_not_always_defined_in_cond, macro_define, macro_dump, variable_defined, variable_conditions_recursive, variable_conditions, target_conditions, variable_conditionally_defined, variable_conditions_recursive_sub, check_variable_defined_unconditionally, variable_value_as_list, variable_value_as_list_recursive_worker, variable_output, variable_pretty_output, rule_define, append_exeext, am_install_var, require_variables_for_macro): Adjust to use ConditionalSet.