Support $displayb/o/h, $writeb/o/h (starter project)

[veripoolbot]

---

Author Name: Wilson Snyder (@wsnyder)
Original Redmine Issue: 1637 from https://www.veripool.org

---

Good starter project is to implement $displayb/o/h and $writeb/o/h. Add the tests, parsing in verilog.l/verilog.y, then probably can just pass a new type to the AstDisplay node so that when it currently defaults to constructs a %d format it will instead use b/o/h.