New build system

Using new build script system for all platforms. 

- `openssl-sys` prototype taken [alexcricton's repo](https://github.com/alexcrichton/openssl-sys) but embedded as it should be much easier to develop while it's in-tree rather than in a separate repo. 

- dropped all external links but Windows ones. I'm not sure how it is correct to proceed here as don't have access to Windows. Perhaps they could be dropped too as almost every windows app will be linked against `gdi32` and `win32`, `wsock32` may be not.
Which is to say, this is forcing a dynamic linkage against the `gdi32` and `wsock32` libraries, which is *probably* what everyone wants, but you never know!