plugin: Add "clapperglimport" element

A Clapper import element that imports GStreamer `GLMemory` into `GdkTexture` for improved performance where OpenGL is available

lib/gst/plugin/gstclapperglimport.h

@@ -0,0 +1,38 @@
+/*
+ * Copyright (C) 2022 Rafał Dzięgiel <rafostar.github@gmail.com>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Library General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * Library General Public License for more details.
+ *
+ * You should have received a copy of the GNU Library General Public
+ * License along with this library; if not, write to the
+ * Free Software Foundation, Inc., 51 Franklin St, Fifth Floor,
+ * Boston, MA 02110-1301, USA.
+ */
+
+#pragma once
+
+#include "gstclapperglbaseimport.h"
+
+G_BEGIN_DECLS
+
+#define GST_TYPE_CLAPPER_GL_IMPORT (gst_clapper_gl_import_get_type())
+G_DECLARE_FINAL_TYPE (GstClapperGLImport, gst_clapper_gl_import, GST, CLAPPER_GL_IMPORT, GstClapperGLBaseImport)
+
+#define GST_CLAPPER_GL_IMPORT_CAST(obj)        ((GstClapperGLImport *)(obj))
+
+struct _GstClapperGLImport
+{
+  GstClapperGLBaseImport parent;
+};
+
+GST_ELEMENT_REGISTER_DECLARE (clapperglimport);
+
+G_END_DECLS