windows: install header files required for compiled addons

[piscisaureus]

The windows installer should install header files. If we do this node-gyp wouldn't have to download a tarball to get the headers.
I would suggest to install them into program files\iojs\include.

[sam-github]

+ a bunch, needing proxy access to external internet in order to just compile a c++ addon is onerous.

[mscdex]

+1

[cjihrig]

👍

[piscisaureus]

I can do it myself, but this is also a reasonably simple patch that can be implemented by another contributor.

[Trott]

Forgive me if this is a naïve question, but does this basically involve opening tools/msvs/msi in Visual Studio and adding the header files there?

[Trott]

@piscisaureus @nodejs/build Should this remain open?

[gibfahn]

I think this can be closed in favour of nodejs/node-gyp#1247, if we embed the headers in the binary then there's no need to have them separately in the installer.