Give missing -lz hint when looking for png.  Needed for static png libraries and strict linking.
Give missing -lz hint when looking for png.  Needed for static png libraries and strict linking.

pcqpcq/sox,uklauer/sox,jacksonh/sox,CaptainHayashi/sox,jacksonh/sox,davel/sox,Motiejus/sox,Motiejus/sox,mhartzel/sox_personal_fork,uklauer/sox,CaptainHayashi/sox,CaptainHayashi/sox,cbagwell/sox,pcqpcq/sox,MageSlayer/sox,pcqpcq/sox,MageSlayer/sox,Motiejus/sox,MageSlayer/sox,pcqpcq/sox,davel/sox,MageSlayer/sox,Motiejus/sox,jacksonh/sox,MageSlayer/sox,CaptainHayashi/sox,uklauer/sox,Distrotech/sox,uklauer/sox,Distrotech/sox,mhartzel/sox_personal_fork,cbagwell/sox,mhartzel/sox_personal_fork,jacksonh/sox,cbagwell/sox,Distrotech/sox,davel/sox,davel/sox,cbagwell/sox,mhartzel/sox_personal_fork,Distrotech/sox