patch 9.1.1063: too many strlen() calls in userfunc.c

patch 9.1.1063: too many strlen() calls in userfunc.c

Problem:  too many strlen() calls in userfunc.c
Solution: refactor userfunc.c and remove calls to strlen(),
          drop set_ufunc_name() and roll it into alloc_ufunc(),
          check for out-of-memory condition in trans_function_name_ext()
          (John Marriott)

closes: #16537

Signed-off-by: John Marriott <basilisk@internode.on.net>
Signed-off-by: Christian Brabandt <cb@256bit.org>