Implement BVZX case in Simplifier (so that using BVZX will not fail with an exception).
Add BVZX to CVC parser and refactor SMT1/2 parsers to use BVZX.
Merge pull request #31 from khooyp/implement-bvzx-simplifier

Implement BVZX case in Simplifier (so that using BVZX will not fail with an exception).