Clarify versioning comment instructions in configure.ac

configure.ac

@@ -9,14 +9,24 @@ OB_VERSION=$PACKAGE_VERSION
 AC_SUBST(OB_VERSION)
 
 dnl Making releases:
+dnl RR_ is for obrender, OBT_ is for obt, keep major/minor in sync,
+dnl treat the rest separately.
+dnl
+dnl if MAJOR or MINOR version changes, be sure to change AC_INIT above to match.
+dnl the other variables aren't related to the user visible versions, but are used
+dnl to version the .so files.
+dnl if no backward compat is broken, it's just a preference if you want to bump
+dnl the AC_INIT micro version or minor version. if the AC_INIT micro version is
+dnl 0, don't write it out.
+dnl
+dnl How to process .so versioning,
 dnl   RR_MICRO_VERSION += 1;
 dnl   RR_INTERFACE_AGE += 1;
-dnl   R_BINARY_AGE += 1;
+dnl   RR_BINARY_AGE += 1;
 dnl if any functions have been added, set RR_INTERFACE_AGE to 0.
 dnl if backwards compatibility has been broken,
 dnl set RR_BINARY_AGE and RR_INTERFACE_AGE to 0.
-dnl
-dnl if MAJOR or MINOR version changes, be sure to change AC_INIT above to match
+dnl if you set anything to 0, you should also bump the MINOR version.
 dnl
 RR_MAJOR_VERSION=3
 RR_MINOR_VERSION=5