factor: eliminate print_uuint recursion

factor: eliminate print_uuint recursion

* src/factor.c (lbuf_putint_append): New function, with
most of the old lbuf_putint body.  Do the umaxtostr stuff
by hand so that we needn’t worry about the trailing NUL.a
Do the string copy by hand since the string is so short.
(lbuf_putint): Reimplement in terms of lbuf_putint_append.
Omit last arg, which is no longer needed.  All callers changed.
(print_uuint): Rewrite to avoid recursion, using
lbuf_putint_append for the usual case.