[atkmm] Change ABI from atkmm-1.6 to atkmm-2.26

[Murray Cumming <murrayc src gnome org>]

commit 73d52acae6298d3c13b5d132621fe9fa60c9e91f
Author: Murray Cumming <murrayc murrayc com>
Date:   Fri Nov 11 10:26:04 2016 +0100

    Change ABI from atkmm-1.6 to atkmm-2.26
    
    This installs in parallel with atkmm-1.6.

 atk/atkmm.h  |    4 ++--
 configure.ac |    2 +-
 2 files changed, 3 insertions(+), 3 deletions(-)
---
diff --git a/atk/atkmm.h b/atk/atkmm.h
index d593ea9..6824b4d 100644
--- a/atk/atkmm.h
+++ b/atk/atkmm.h
@@ -39,11 +39,11 @@
  * compilation, but suffices for this simple example. Assuming that your
  * program source file is @c program.cc, compile it with:
  * @code
- * g++ program.cc -o program  `pkg-config --cflags --libs atkmm-1.6`
+ * g++ program.cc -o program  `pkg-config --cflags --libs atkmm-2.26`
  * @endcode
  * Alternatively, if using autoconf, use the following in @c configure.ac:
  * @code
- * PKG_CHECK_MODULES([ATKMM], [atkmm-1.6])
+ * PKG_CHECK_MODULES([ATKMM], [atkmm-2.26])
  * @endcode
  * Then use the generated @c ATKMM_CFLAGS and @c ATKMM_LIBS variables in
  * the project @c Makefile.am files. For example:
diff --git a/configure.ac b/configure.ac
index 2260617..3f35175 100644
--- a/configure.ac
+++ b/configure.ac
@@ -36,7 +36,7 @@ AM_MAINTAINER_MODE
 AC_ARG_VAR([ACLOCAL_FLAGS], [aclocal flags, e.g. -I <macro dir>])
 
 MM_PREREQ([0.9.10])
-MM_INIT_MODULE([atkmm-1.6])
+MM_INIT_MODULE([atkmm-2.26])
 
 # Copy the mm-common .pl scripts into doc/, and use them from there,
 # so we can dist them to avoid a tarball-build dependency.