Problem: OBS _service sets version to unix timestamp.commitid

Solution: a new option has been added to the tar_scm service, so use
it to set the version to last_tag+git<last commit date> which is more
useful.
Unfortunately it's not possible to set it to the current version as
set in the header files, as it's not possible to parse files, only
commit ids, dates and git tags. But it's a step forward.

packaging/obs/_service

@@ -2,7 +2,9 @@
   <service name="tar_scm">
     <param name="url">https://github.com/zeromq/libzmq</param>
     <param name="scm">git</param>
-    <!--<param name="versionformat">@PARENT_TAG@+git%cd</param>-->
+    <param name="versionformat">@PARENT_TAG@+git%cd</param>
+    <param name="versionrewrite-pattern">v(.*)</param>
+    <param name="versionrewrite-replacement">\1</param>
     <param name="exclude">.git</param>
     <param name="changesgenerate">enable</param>
     <param name="filename">zeromq</param>