[gtkmm] Gdk::TimeCoord: Don't use the deprecated g_memdup()

[Kjell Ahlstedt <kjellahl src gnome org>]

commit b8f767f563f91ef70093afc064a33ef09a292313
Author: Kjell Ahlstedt <kjellahlstedt gmail com>
Date:   Tue Feb 16 09:58:08 2021 +0100

    Gdk::TimeCoord: Don't use the deprecated g_memdup()

 gdk/src/timecoord.ccg | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)
---
diff --git a/gdk/src/timecoord.ccg b/gdk/src/timecoord.ccg
index b25464c7..dde34bb4 100644
--- a/gdk/src/timecoord.ccg
+++ b/gdk/src/timecoord.ccg
@@ -23,8 +23,14 @@ namespace
 
 inline GdkTimeCoord* time_coord_copy(const GdkTimeCoord* gobject)
 {
-  // If gobject == nullptr, g_memdup() returns nullptr.
-  return static_cast<GdkTimeCoord*>(g_memdup(gobject, sizeof(GdkTimeCoord)));
+  // Don't use g_memdup(). It's deprecated in glib 2.67.3.
+  // Its replacement, g_memdup2(), is new in glib 2.67.3.
+  if (!gobject)
+    return nullptr;
+
+  GdkTimeCoord* new_obj = g_new(GdkTimeCoord, 1);
+  *new_obj = *gobject;
+  return new_obj;
 }
 
 } // anonymous namespace