Explicitly mark so_version so we know when there's an API compatibility break

Signed-off-by: Michel Alexandre Salim <salimma@fedoraproject.org>

rubberband.spec

@@ -1,3 +1,5 @@
+%global so_version 2
+
 Name:           rubberband
 Version:        3.0.0
 Release:        %autorelease
@@ -61,7 +63,7 @@ rm -rf $RPM_BUILD_ROOT%{_libdir}/*.a
 %doc README.md
 %{_bindir}/rubberband
 %{_bindir}/rubberband-r3
-%{_libdir}/*.so.*
+%{_libdir}/*.so.%{so_version}*
 %{_libdir}/ladspa/ladspa-rubberband.*
 %{_libdir}/lv2/rubberband.lv2/*
 %{_datadir}/ladspa/rdf/ladspa-rubberband.rdf