Speedup Automake::DisjConditions::invert().

Speedup Automake::DisjConditions::invert().
* lib/Automake/Condition.pm (multiply): New.
* lib/Automake/DisjConditions.pm (_multiply): Use it.
(sub_conditions): Likewise.

* lib/Automake/Condition.pm (reduce): Rename to ...
(reduce_and): ... this.
(reduce_or): New.
* lib/Automake/DisjConditions.pm (_multiply): Use reduce_or().
* lib/Automake/tests/Condition.pl (test_reduce): Rename to ...
(test_reduce_and): ... this.
(test_reduce_or): New.
* lib/Automake/tests/DisjConditions.pl
(test_invert): Update to reflect effect of reduce_or().
(test_simplify): Don't skip invert() on larger inputs.