This fixes several issues with the implied operators when NEW_MATH is enabled:
* None of the implied operators were returning the correct value, which should be the value
assigned to the LHS.
* The &&=, ||= ad ^^= operators were also operating on uninitialized variables and so behaving
unpredictably.
* The /= and %= operators would crash the client when the RHS was zero, because after outputting
the "Divide by zero" error they would go on to perform the operation anyway.
