Don't build print-number-table unless it will be used

Don't build print-number-table unless it will be used

There are only a few users of print-number-table, and none of them use
it when print-circle is nil.  A couple of them used to.  print_object
was changed in 2012-04-20 "* src/print.c (print_preprocess): Only
check print_depth if print-circle is nil".
byte-compile-output-docform which uses print-number-table binds
print-circle to t before printing unless
byte-compile-disable-print-circle is set, but that variable has been
marked obsolete since 24.1.

* src/print.c (print_preprocess): Assert Vprint_circle is non-nil.
Remove code handling the case when Vprint_circle is nil.
(print, Fprint_preprocess): Don't call print_preprocess unless
Vprint_circle is non-nil.
(print_object): Remove comment referencing removed code in
print_preprocess.