Force the SONAME of libtonezone to be 2.0

For backward compatibility reasons, the SONAME of libtonezone can't just
be 2 (autotools' standard). It should be 2.0.

This adds soname.patch.

debian/patches/series

@@ -2,3 +2,4 @@ zaptel_perl
 echocan_oslec
 init_unload_oslec
 remove_dahdi_speed
+soname.patch

debian/patches/soname.patch

@@ -0,0 +1,11 @@
+diff --git a/configure.ac b/configure.ac
+index 826a7ec..2afe476 100644
+--- a/configure.ac
++++ b/configure.ac
+@@ -392,5 +392,6 @@ AC_CONFIG_FILES([
+ 	xpp/perl_modules/Makefile
+ 	])
+ AC_OUTPUT
++sed -i -e '/^soname_spec=/s/major/&.\\$revision/' libtool
+ 
+ AC_MSG_NOTICE(*** dahdi-tools build successfully configured ***)

debian/rules

@@ -57,6 +57,9 @@ else
 	$(MAKE) clean
 endif
 
+override_dh_auto_configure:
+	dh_auto_configure
+
 override_dh_auto_install:
 	# also run the 'config' target, in addition to the 'install' target:
 	dh_auto_install -- config