Check return value of waitpid. Don't evaluate status of children if waitpid

wasn't successful.
Henning Meier-Geinitz <henning@meier-geinitz.de>

doc/descriptions/mustek.desc

@@ -9,7 +9,7 @@
 ;
 
 :backend "mustek"		; name of backend
-:version "1.0-122"		; version of backend
+:version "1.0-123"		; version of backend
 :status :stable			; :alpha, :beta, :stable, :new
 :manpage "sane-mustek"		; name of manpage (if it exists)
 :url "http://www.meier-geinitz.de/sane/"