Enable the rest of the division tests

Before:
```
$ ./expand2
Expanding: ((y + x + z + w)^15 + w)*(y + x + z + w)^15
1538ms
number of terms: 6272
```
After (d4cd00d0b1f63f0726183f997729ac8a7f4786eb):
```
$ ./expand2
Expanding: ((y + x + z + w)^15 + w)*(y + x + z + w)^15
1770ms
number of terms: 6272
```
So something got slower in this PR.
At e5ec14f4e4b47918aca5cb25fb475656955c801f:
```
$ ./expand2
Expanding: ((y + x + z + w)^15 + w)*(y + x + z + w)^15
1570ms
number of terms: 6272
```