libmpg123-shlibs package need to have libtool2-shlis in its Depends: field.
retinapro:~ ichiro$ otool -L /sw/lib/libmpg123.0.dylib
/sw/lib/libmpg123.0.dylib:
/sw/lib/libmpg123.0.dylib (compatibility version 41.0.0, current version 41.1.0)
/sw/lib/libltdl.7.dylib (compatibility version 11.0.0, current version 11.0.0)
/usr/lib/libSystem.B.dylib (compatibility version 1.0.0, current version 1197.1.1)
retinapro:~ ichiro$ dpkg -s libmpg123-shlibs
Package: libmpg123-shlibs
Status: install ok installed
Priority: optional
Section: sound
Installed-Size: 404
Maintainer: Daniel Johnson daniel@daniel-johnson.org
Architecture: darwin-x86_64
Source: mpg123
Version: 1:1.19.0-1
Depends: darwin (>= 13-1)
Assigning to mpg123 maintainer.
Good catch. I've now fixed it.
Thanks.