Take into account environment size when calculating ARG_MAX.
Take into account environment size when calculating ARG_MAX.

http://www.in-ulm.de/~mascheck/various/argmax/ has some
discussion about it.

Hopefully addresses #1061.

mjafin/bcbio-nextgen,guillermo-carrasco/bcbio-nextgen,vladsaveliev/bcbio-nextgen,a113n/bcbio-nextgen,chapmanb/bcbio-nextgen,biocyberman/bcbio-nextgen,guillermo-carrasco/bcbio-nextgen,lpantano/bcbio-nextgen,brainstorm/bcbio-nextgen,chapmanb/bcbio-nextgen,chapmanb/bcbio-nextgen,a113n/bcbio-nextgen,mjafin/bcbio-nextgen,mjafin/bcbio-nextgen,vladsaveliev/bcbio-nextgen,Cyberbio-Lab/bcbio-nextgen,biocyberman/bcbio-nextgen,lbeltrame/bcbio-nextgen,brainstorm/bcbio-nextgen,Cyberbio-Lab/bcbio-nextgen,lbeltrame/bcbio-nextgen,brainstorm/bcbio-nextgen,gifford-lab/bcbio-nextgen,gifford-lab/bcbio-nextgen,a113n/bcbio-nextgen,biocyberman/bcbio-nextgen,gifford-lab/bcbio-nextgen,vladsaveliev/bcbio-nextgen,lbeltrame/bcbio-nextgen,lpantano/bcbio-nextgen,Cyberbio-Lab/bcbio-nextgen,guillermo-carrasco/bcbio-nextgen,lpantano/bcbio-nextgen