[gtkmm-documentation] Use glibmm-2.54 instead of glibmm-2.52

[Murray Cumming <murrayc src gnome org>]

commit ea9556d92917a3d8fd6eb420c370ced58ef55031
Author: Murray Cumming <murrayc murrayc com>
Date:   Wed Mar 22 11:31:28 2017 +0100

    Use glibmm-2.54 instead of glibmm-2.52
    
    We changed the ABI name.

 configure.ac |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index 46f6c89..70d8c1c 100644
--- a/configure.ac
+++ b/configure.ac
@@ -25,7 +25,7 @@ MM_AX_CXX_COMPILE_STDCXX([14], [noext], [mandatory])
 AC_PATH_PROG([PERL], [perl], [perl])
 AC_PROG_SED
 
-PKG_CHECK_MODULES([GIOMM], [giomm-2.52 >= 2.51.1])
+PKG_CHECK_MODULES([GIOMM], [giomm-2.54 >= 2.51.1])
 PKG_CHECK_MODULES([GTKMM], [gtkmm-4.0  >= 3.89.0])
 MM_PKG_CONFIG_SUBST([GTHREAD_CFLAGS], [--cflags-only-other gthread-2.0])