Add Obsoletes to better handle upgrade path from before -libs was introduced

Could theoretically replace the 2 obsoletes with a single
Conflicts: gdbm < 1:1.14.1-4
in -libs, but I think Obsoletes approach more closely follows
https://fedoraproject.org/wiki/Upgrade_paths_%E2%80%94_renaming_or_splitting_packages
in spirit

gdbm.spec

@@ -3,7 +3,7 @@
 Summary: A GNU set of database routines which use extensible hashing
 Name: gdbm
 Version: 1.18
-Release: 1%{?dist}
+Release: 2%{?dist}
 Epoch: 1
 License: GPLv3+
 URL: http://www.gnu.org/software/gdbm/
@@ -23,6 +23,10 @@ BuildRequires: gcc
 BuildRequires: libtool
 BuildRequires: gettext
 BuildRequires: readline-devel
+
+# when -libs subpkg was introduced
+Obsoletes: gdbm < 1:1.14.1-4
+
 Requires: %{name}-libs%{?_isa} = %{epoch}:%{version}-%{release}
 
 %description
@@ -38,6 +42,8 @@ install gdbm-devel.
 
 %package libs
 Summary: Libraries files for gdbm
+# when -libs subpkg was introduced
+Obsoletes: gdbm < 1:1.14.1-4
 
 %description libs
 Libraries for the Gdbm GNU database indexing library
@@ -125,6 +131,9 @@ fi
 %{_mandir}/man3/* 
 
 %changelog
+* Mon Oct 01 2018 Rex Dieter <rdieter@fedoraproject.org> - 1.18-2
+- Add Obsoletes to better handle upgrade path from before -libs was introduced
+
 * Tue Sep 25 2018 mskalick@redhat.com
 - Rebase to latest release 1.18
 - Fix issues found by coverity