There are several ways to name libs:
- Solaris-style: .so -> .so.1
- GNU style: .so -> .so.1 -> .so.1.2.3
- Random: .so -> .so.1.2
See:
https://blogs.oracle.com/ali/entry/how_to_name_a_solaris
http://www.gnu.org/software/libtool/manual/libtool.html#Versioning