Implement symbol versioning


diff --git a/Makefile.am b/Makefile.am
index 54efe9e..288cd65 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -23,6 +23,8 @@
 
 MODULECOMMONFLAGS = -no-undefined -export-symbols-regex ".*" -shared -module -avoid-version
 
+SUBDIRS = .
+
 # Options to pass when running configure in the distcheck target.
 #
 # We want to preserve user-provided option variables so the same