Compare results of expression simplifier on vs. off

[artemdinaburg]

We now handle many expression simplifications at the anvill level.

Do we still need an expression simplifier, since it occasionally fails?

Lets do the following:

1. Make the expression simplifier on or off via a flag (--simplify-expressions)
2. Run on Angha with --simplify-expressions
3. Run on Angha w/o --simplify-expressions
4. Do a diff of the output C and make a decision whether to default it to on or off, or to limit scope in some way to avoid the error conditions.