hook up repo versions of png/zlib/jpeg for bpgenc/bpgdec
hook up repo versions of png/zlib/jpeg for bpgenc/bpgdec

jasongorski/libbpg-xcode,jasongorski/libbpg-xcode,jasongorski/libbpg-xcode,jasongorski/libbpg-xcode,jasongorski/libbpg-xcode,jasongorski/libbpg-xcode,jasongorski/libbpg-xcode