Added "os/wait.hpp" to stout's "os.hpp" header.
Added "os/wait.hpp" to stout's "os.hpp" header.

Review: https://reviews.apache.org/r/52899/

gsantovena/mesos,kaysoky/mesos,neilconway/mesos,craimbert/mesos,chhsia0/mesos,craimbert/mesos,dforsyth/mesos,asamerh4/mesos,craimbert/mesos,jpeach/mesos,kaysoky/mesos,Gilbert88/mesos,craimbert/mesos,chhsia0/mesos,reneploetz/mesos,abudnik/mesos,gsantovena/mesos,Aman-Jain-14/customizedMesos,yuquanshan/customizedMesos,reneploetz/mesos,yuquanshan/customizedMesos,reneploetz/mesos,verizonlabs/mesos,Gilbert88/mesos,abudnik/mesos,asamerh4/mesos,zmalik/mesos,abudnik/mesos,dforsyth/mesos,gsantovena/mesos,neilconway/mesos,Aman-Jain-14/customizedMesos,Aman-Jain-14/customizedMesos,chhsia0/mesos,andschwa/mesos,asamerh4/mesos,verizonlabs/mesos,zmalik/mesos,andschwa/mesos,chhsia0/mesos,reneploetz/mesos,yuquanshan/customizedMesos,neilconway/mesos,Gilbert88/mesos,Gilbert88/mesos,andschwa/mesos,verizonlabs/mesos,zmalik/mesos,yuquanshan/customizedMesos,verizonlabs/mesos,kaysoky/mesos,kaysoky/mesos,andschwa/mesos,asamerh4/mesos,jpeach/mesos,dforsyth/mesos,verizonlabs/mesos,abudnik/mesos,kaysoky/mesos,abudnik/mesos,chhsia0/mesos,zmalik/mesos,dforsyth/mesos,Aman-Jain-14/customizedMesos,reneploetz/mesos,verizonlabs/mesos,Aman-Jain-14/customizedMesos,craimbert/mesos,jpeach/mesos,kaysoky/mesos,asamerh4/mesos,verizonlabs/mesos,Aman-Jain-14/customizedMesos,abudnik/mesos,zmalik/mesos,andschwa/mesos,reneploetz/mesos,neilconway/mesos,reneploetz/mesos,yuquanshan/customizedMesos,jpeach/mesos,asamerh4/mesos,Gilbert88/mesos,craimbert/mesos,jpeach/mesos,yuquanshan/customizedMesos,andschwa/mesos,dforsyth/mesos,Gilbert88/mesos,neilconway/mesos,Aman-Jain-14/customizedMesos,neilconway/mesos,craimbert/mesos,gsantovena/mesos,dforsyth/mesos,zmalik/mesos,gsantovena/mesos,andschwa/mesos,jpeach/mesos,gsantovena/mesos,asamerh4/mesos,gsantovena/mesos,neilconway/mesos,chhsia0/mesos,chhsia0/mesos,yuquanshan/customizedMesos,kaysoky/mesos,zmalik/mesos,dforsyth/mesos,abudnik/mesos,Gilbert88/mesos,jpeach/mesos