Add vprint_debug to show what requirements are being compared

Requested by @todb-r7 

Verification Steps:

- [x] Set up a Win XP SP3 box with IE8
- [x] Use the ```exploit/windows/browser/ms13_090_cardspacesigninhelper``` exploit
- [x] Do: ```set verbose true```
- [x] Let the exploit run against the vuln host. You should see requirements being compared.