We now use ints, and hopefully this means we don't have as much obvious
stuff in the binaries!
```
$ # Before:
$ strings metsrv.x86.dll | grep core_ | wc -l
46
$ # After:
$ strings metsrv.x86.dll | grep core_ | wc -l
0
```
Big win, and it's even bigger for the likes of stdapi.
Had to fix a bunch of other stuff along the way, including a subtle
issue with the Powershell Meterp bindings.
The 'common' library has been removed. The only project that actually
used it was metsrv, so the code that metsrv required from common is now
directly compiled in as part of that project.
The common folder now contains files that are importanta cross all of
the projects, with a primary focus on the new "API" style function. What
this means is that MetSrv has an API that it exposes through a function
pointer that is passed to the extension when it's initialised. This
pointer references a structure with all the API functions wired in. This
means that:
* Extensions don't need to know anything about metsrv at compile time.
* The delay loading code can be removed, which was one of the last
instances of "metsrv.dll" as a string.
* Metsrv.dll no longer exports any functions.
More to come.
