newfun - add a name in the table of functions
Utility function (for experts only). Adds the name "function-name" in the table of functions known to the interpreter. "nameptr" is an integer 100*fun+fin where fun and fin is the internal coding of the primitive "function-name" . This function is useful to associate a primitive to a routine interfaced in "matusr.f" ( fun=14 ). Used with funptr and clearfun one can redefine a primitive by a function with same name.