Rb_set_kcode equivalent for 1.9.x

The C function rb_set_kcode was defined in the 1.8.x branch.

In the 1.9.x branch, the encoding was overhauled, and all the methods
were renamed (without aliasing, it seems.)

I use an application than loads the Ruby interpreter (as a scripting
engine.) It loads 1.8.x fine, but cannot load 1.9.x (“rb_set_kcode entry
point not found” or similar error occurs.)

The application calls rb_set_kcode to set encoding to UTF8.

I’d like to inform the software company of the new call for 1.9.x, can
anyone tell me what the correct call would be to set encoding to UTF8 in
1.9.x ??

P.S. - I need the C function call not the Ruby call, not the Ruby
command line argument -K.

It’s something like rb_enc_somefunction_name( arg )