New headers and parameters from RFC 3455 and UUI drafts

These changes derive from mail by John Gregg (see http://list.resiprocate.org/archive/resiprocate-devel/msg08665.html). I added additional header to exchange User-to-User information via SIP.
I agree it is helpful to provide something convenient for Windows users.

Maybe I can just tweak the build scripts so that they always ignore the generated files and regenerate them on every build.  This will mean Linux users can ignore the files in the repository.  However, it still means that Windows users would need to scrutinize any changes that come in through Github pull requests.  In theory, somebody could submit a generated file that has been tampered with and it would be very hard for somebody reviewing the diff to spot that.

Another solution might be creating a branch or a git submodule for generated files.