Dll support: testers needed

[rikki cattermole]

+infinity

Few things I would like answered:

- Why -useShared and not -fPIC?
   - If -useShared why not use it on *nix to turn on -fPIC?
- Why isn't DllIsUsedFromC.no automatically detected?

Regarding C-runtime, yes we need to distribute every version that we 
support on Windows. The compiler will pick the latest (or the installer 
I guess) to use, but we should be able to switch between them. Either 
that or we ship a static lib of Phobos to be linked into a dll upon 
first request of a specific C-runtime.