Adds support for go.
Refactored jit script, exports binaries (especially go)

Instead of a single jit script we now have a collection of jit scripts,
that are driven by one include file. You no longer use

    #!../jit cc

instead you use

    #!../jit.cc

This change allows, amongst other things, binaries in well-known, public
places. This is mostly interesting for go scripts, that can now be
cross-compiled and distributed along with the scripts source code.
Updates documentation