Bump soname version to match the 1.0.x branch.

Library soname versioning is something we normally change
only right before each release. However, with 1.0.2 being
released from the 1.0.x branch with 3.0.3, it makes sense
to make the same update here. That way when we do a new
release from master we can just increment again and have
the version properly reflect ranges relative to the stable
branch.