contrib: integrate RPM spec

Remove OpenSUSE bug report link, set version to @VERSION@, make it build with
CentOS 8 etc.

Related: OS#4550
Change-Id: I3e135e5e7807688366598a24e121550d6292906c
diff --git a/configure.ac b/configure.ac
index 1e9cb26..f095cf5 100644
--- a/configure.ac
+++ b/configure.ac
@@ -167,4 +167,5 @@
 	include/Makefile
 	src/Makefile
 	tests/Makefile
-	Makefile)
+	Makefile
+	contrib/libosmo-abis.spec)