Remove useless opcode handlers

Please take a quick look and let me know if you see any problems.

https://gist.github.com/dstogov/23cc318dd3e411904e10

I'm going to commit this tomorrow.

Thanks. Dmitry.

ZEND_ADD is not commutative for array operands.

Unfortunately, you are right :(

ZEND_MUL may not be commutative if operator overloading is involved (e.g.
matrix multiplication is not abelian).

Right again.

The NO_CONST_CONST cases are problematic: Opcache currently, in my eyes
incorrectly, evaluates constant expressions even if they throw notices
(currently I think mostly by suppressing them). If we do not evaluate
these, we may end up with CONST_CONST operations. (This is not a huge
problem just now because constant folding in opcache is limited -- however
with full constant propagation this leads to many test failures.)

The patch adds NO_CONST_CONST handling to opcache. All tests are passed, I
also didn't see any problems running ~10 real-life apps.

The opcodes affected by the last point (limited to those included in your
patch) are SUB, MUL, POW, CONCAT (array operands) and BW_NOT (various).
However with Andrea's invalid numeric string RFC more will fall in this
category (evaluable but throwing).

I didn't get what is wrong with SUB, MUL, etc, because they are evaluated
at compile-time
Anyway, I see - the patch can't be committed in current state.
Thanks for review.

What I mean is, for example:

var_dump(~(bool)true);
echo "Done\n";

Will throw an exception without opcache, will result in no output (and no
visible error) with opcache. My point here is that const-operand-only
cases might be necessary to handle error cases like this.

Nikita