Provide and document jit_get_reg/jit_unget_reg/jit_live

[Marc Nieper-Wißkirchen]

Dear Paulo,

I would like to gently remind you of documenting the above functions in the manual and to provide them in the public headers.  In earlier threads, you have given a number of use cases of these functions.

Please tell me in case I can help you (for example, by providing a patch).

Thank you,

Marc