Access procedures from runtime/runtime.pkg

[Amirouche]

In collusion with other people, I am trying to build a portable set of 
libraries.

I started with a JSON library (rework of SRFI-180), the current test suite pass
with nine Scheme implementation [0].

Question:

  how can I import procedures that are defined in runtime/runtime.pkg
  e.g. arithmetic-shift or bitwise-ior?

Thanks in advance :)

[0] https://github.com/scheme-live/live/pull/39