[gnome-autoar] configure: provide soname

[Carlos Soriano Sánchez <csoriano src gnome org>]

commit 848a42aa4cec62444c3e273365b81289c0bee583
Author: Carlos Soriano <csoriano gnome org>
Date:   Tue Aug 23 14:22:38 2016 +0200

    configure: provide soname
    
    We were missing soname versioning, which is necessary for distributions.
    
    Thanks Michael Catanzaro for the help.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=770275

 configure.ac |   10 ++++++++++
 1 files changed, 10 insertions(+), 0 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index 7cac822..2366a66 100644
--- a/configure.ac
+++ b/configure.ac
@@ -18,6 +18,16 @@ AM_INIT_AUTOMAKE([1.11 foreign dist-xz no-dist-gzip tar-ustar subdir-objects])
 AM_MAINTAINER_MODE([enable])
 m4_ifdef([AM_SILENT_RULES], [AM_SILENT_RULES([yes])])
 
+# reset to 0 at the beginning of a development cycle
+# increment by 1 for every stable micro release
+m4_define([interface_age], [0])
+m4_define([binary_age], [m4_eval(100 * minor_version + micro_version)])
+m4_define([lt_current], [m4_eval(binary_age - interface_age)])
+m4_define([lt_revision], [interface_age])
+m4_define([lt_age], [m4_eval(binary_age - interface_age)])
+
+AC_SUBST([LIBGNOME_AUTOAR_LT_VERSION], [lt_current:lt_revision:lt_age])
+
 AC_PROG_CC
 AC_PROG_CC_STDC
 AC_PROG_INSTALL