Fix to empty response to (get-assignment).

Thanks to David Cok for reporting this issue.
Fixed "success" response to (push N) / (pop N) with N > 1.

Thanks to David Cok for reporting this issue.
Disallow construction of (_ BitVec 0).

Thanks to David Cok for reporting this issue.
A couple of fixes to the get-option command for compliance with SMT-LIB.

Thanks to David Cok for reporting this issue.
Better error on illegal (pop N); also more compliant SMT-LIB error messages in some places

Thanks to David Cok for reporting these issues.
Better error on invalid logic strings.

Thanks to David Cok for reporting this issue.
Fix destruction issue in GetValueCommand leading to crash.

Thanks to David Cok for reporting this.
Fix for equality-chaining of Booleans in SMT-LIBv2.

Thanks to David Cok for reporting this.
As per SMT-LIB standard: make - and xor take n>2 args and be left-assoc; => takes n>2 args and is right-assoc.

Thanks to David Cok for pointing out this issue.
Don't allow --stats if not a statistics-enabled build
fix arithmetic error reporting on use of (nonlinear) div,mod,/ symbols