build: Rename gobjectenumtypes.[ch] to glib-enumtypes.[ch]

To reflect the fact that they contain the GObject types for various
enums defined in libglib.

See https://gitlab.gnome.org/GNOME/glib/merge_requests/481#note_451086.

Signed-off-by: Philip Withnall <withnall@endlessm.com>

Helps: GNOME/gobject-introspection#267

gobject/glib-enumtypes.c.template

@@ -0,0 +1,38 @@
+/*** BEGIN file-header ***/
+#include "config.h"
+#include "glib-enumtypes.h"
+#include <glib-object.h>
+
+/*** END file-header ***/
+
+/*** BEGIN file-production ***/
+/* enumerations from "@filename@" */
+/*** END file-production ***/
+
+/*** BEGIN value-header ***/
+GType
+@enum_name@_get_type (void)
+{
+  static volatile gsize g_define_type_id__volatile = 0;
+
+  if (g_once_init_enter (&g_define_type_id__volatile))
+    {
+      static const G@Type@Value values[] = {
+/*** END value-header ***/
+
+/*** BEGIN value-production ***/
+        { @VALUENAME@, "@VALUENAME@", "@valuenick@" },
+/*** END value-production ***/
+
+/*** BEGIN value-tail ***/
+        { 0, NULL, NULL }
+      };
+      GType g_define_type_id =
+        g_@type@_register_static (g_intern_static_string ("@EnumName@"), values);
+      g_once_init_leave (&g_define_type_id__volatile, g_define_type_id);
+    }
+
+  return g_define_type_id__volatile;
+}
+
+/*** END value-tail ***/