This test verifies that M62-M68 can be remapped through both python and NGC, and that calling the original M-codes is supported in the remap subroutine. It also serves as an example of how to do this, since esp. the M66 python function is not trivial and must be a generator yielding `INTERP_EXECUTE_FINISH`. The recursive call to the original functions needs supporting code for mode 5 M-codes in `interp_convert.cc` `convert_m()`, and for M62-M68 in `rs274ngc_pre.cc`, `find_remappings()`. The peculiar M66 needs special handling in the interpreter for `input_flag`, and to ensure that its result (in param `#5399`) is available within the remap, `Interp::pycall()` runs `read_inputs()` before returning control back to the python generator.