Get rid of callcc

[SeeRM 8407]
Add support for stdapi_net_resolve_host.
Add fault tolerance for resolve_hosts.
Fix ropdb spec according to @limhoff-r7's comments
Use a named subject
Add module for the vbulletin exploit in the wild
Clean module and add reporting
Return nil on error, and move the module to post/multi.
Remove windows from title of multi module.
Land #2453, Add stdapi_net_resolve_host(s) to Python Meterpreter.

Moves resolve_host post module to multi and depreciates Windows module.
Resolve will now return nil for failed lookups instead of an empty
string.
Land #2413, axe callcc

This is the only time callcc is used in the entire codebase, too, so
this apparently removes a roadblack to non-MRI Rubies, so that's nice.
Land #2477, add specs for ROPDB
Minor updates to vbulletin admin exploit
Land #2493, vbulletin exploit