Use m4_esyscmd_s to determine AC_REVISION. Closes: #841459

debian/patches/re-autoconfig.patch

@@ -23,7 +23,7 @@ Last-Update: 2016-07-20
 --- /dev/null
 +++ b/configure.ac
 @@ -0,0 +1,43 @@
-+AC_REVISION([m4_esyscmd([dpkg-parsechangelog -SVersion])])
++AC_REVISION([m4_esyscmd_s([dpkg-parsechangelog -SVersion])])
 +
 +AC_INIT([libbgpdump], 1.4.99.15, [ris@ripe.net])
 +