[glibmm] Use libsigc++-3.0.tag for libsigc++ documentation

[Kjell Ahlstedt <kjellahl src gnome org>]

commit 1f9a039e002dfb06dcafb56a3dd024169b9c79af
Author: Kjell Ahlstedt <kjellahlstedt gmail com>
Date:   Thu Apr 26 15:59:16 2018 +0200

    Use libsigc++-3.0.tag for libsigc++ documentation

 configure.ac |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index 9c9bbb2..5ee14f3 100644
--- a/configure.ac
+++ b/configure.ac
@@ -129,7 +129,7 @@ GLIBMM_C_STD_TIME_T_IS_NOT_INT32
 
 MM_ARG_ENABLE_DOCUMENTATION
 MM_ARG_WITH_TAGFILE_DOC([libstdc++.tag], [mm-common-libstdc++])
-MM_ARG_WITH_TAGFILE_DOC([libsigc++-2.0.tag], [sigc++-2.0])
+MM_ARG_WITH_TAGFILE_DOC([libsigc++-3.0.tag], [sigc++-3.0])
 
 # Check whether --enable-debug-refcounting was given.
 GLIBMM_ARG_ENABLE_DEBUG_REFCOUNTING