*: code shrink and better "died from signal" reporting from wait4pid

*: code shrink and better "died from signal" reporting from wait4pid

function                                             old     new   delta
parse                                                964     967      +3
udhcp_run_script                                     670     665      -5
singlemount                                          911     906      -5
mount_it_now                                         360     355      -5
inotifyd_main                                        521     516      -5
xspawn                                                21       -     -21
------------------------------------------------------------------------------
(add/remove: 0/1 grow/shrink: 1/4 up/down: 3/-41)             Total: -38 bytes

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