expand: use printable_string instead of hard-coding implementation

function                                             old     new   delta
expand_main                                          709     690     -19

Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
do not fail build if MAXSYMLINKS isn't defined

This is needed for, eg, hurd, which is known to have no constraints.

Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
killall5: return 2 if no processes got killed

function                                             old     new   delta
kill_main                                            943     992     +49

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
kill[all[5]]: code shrink

function                                             old     new   delta
kill_main                                            992     947     -45

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>