Bump soname major version in CMakeLists.txt.
diff --git a/CMakeLists.txt b/CMakeLists.txt
index ddbaca1..0c8bf81 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -63,8 +63,8 @@
# libarchive 2.8 == interface version 10 = 2 + 8
# libarchive 2.9 == interface version 11 = 2 + 9
# libarchive 3.0 == interface version 12
-# libarchive 3.x == interface version 12 + x
-math(EXPR INTERFACE_VERSION "12 + ${_minor}")
+# libarchive 3.1 == interface version 13
+math(EXPR INTERFACE_VERSION "13 + ${_minor}")
# Set SOVERSION == Interface version
# ?? Should there be more here ??