This started as an optimization patch, but my first optimization
revealed a bug. In chasing the bug, I found more optimization.
Changes:
1. Eliminate tuples in preprocessing. (opt)
2. Handle CStore in tuple elimination pass. (bugfix)
3. Use tuples instead of arrays in a few more extension ops: (opt)
* GCD for vanishing polynomials and their derivatives
* sorting in transcript checking
4. A few logging revisions