Add waitpid({x|x<-1 or x=0},...) and checking of parent-child relationships
Add waitpid({x|x<-1 or x=0},...) and checking of parent-child relationships

Add support for waitpid(x,...) where x<-1 (wait by pgid) or x=0 (wait by pgid
for current process pgid). Also, check that only parents can call setpgid()
or waitpid().

BUG=None
R=binji@chromium.org, bradnelson@google.com

Review URL: https://codereview.chromium.org/497883002

git-svn-id: 84b3587ce119b778414dcb50e18b7479aacf4f1d@1580 7dad1e8b-422e-d2af-fbf5-8013b78bd812

kuscsik/naclports,Schibum/naclports,dtkav/naclports,dtkav/naclports,yeyus/naclports,dtkav/naclports,yeyus/naclports,dtkav/naclports,Schibum/naclports,kuscsik/naclports,kuscsik/naclports,yeyus/naclports,Schibum/naclports,Schibum/naclports,kuscsik/naclports,yeyus/naclports,kuscsik/naclports,yeyus/naclports,Schibum/naclports,yeyus/naclports,dtkav/naclports,Schibum/naclports