[gimp] autotools, meson: bump GLib dependency to 2.68.0.

[Jehan <jehanp src gnome org>]

commit d707e4cb1a2c763dd00c67529e59ed911f8d92e9
Author: Jehan <jehan girinstud io>
Date:   Thu Aug 26 16:57:07 2021 +0200

    autotools, meson: bump GLib dependency to 2.68.0.
    
    GLib 2.68.0 was released on 2021-03-18 and has finally been added to
    Debian testing (now that the release freeze is over!). So dependency
    bumps are slowly going to happen again on the development branch.
    Actually Debian testing has even 2.68.4, but it's a bit too recent and
    2.68.0 is enough to get rid of some of the deprecation issues.

 configure.ac | 2 +-
 meson.build  | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index 92b5e6bfd6..a725893ae8 100644
--- a/configure.ac
+++ b/configure.ac
@@ -64,7 +64,7 @@ m4_define([gegl_micro_version], [30])
 m4_define([gegl_required_version],
           [gegl_major_minor_version.gegl_micro_version])
 m4_define([gexiv2_required_version], [0.10.6])
-m4_define([glib_required_version], [2.56.2])
+m4_define([glib_required_version], [2.68.0])
 m4_define([gtk_mac_integration_required_version], [2.0.0])
 m4_define([gtk_required_version], [3.22.29])
 m4_define([gtkdoc_required_version], [1.0])
diff --git a/meson.build b/meson.build
index 15dafa5610..37ece74f2e 100644
--- a/meson.build
+++ b/meson.build
@@ -345,7 +345,7 @@ gio               = dependency('gio-2.0')
 gio_specific_name = platform_windows ? 'gio-windows-2.0' : 'gio-unix-2.0'
 gio_specific      = dependency(gio_specific_name)
 
-glib_minver       = '2.56.2'
+glib_minver       = '2.68.0'
 glib              = dependency('glib-2.0',           version: '>='+glib_minver)
 
 conf.set('G_DISABLE_DEPRECATED', glib.version().version_compare('>=2.57'))