vaapi: add typedefs for OES_EGL_image extension

OES_EGL_image extension is an OpenGL ES extension and the typedef might
not be available on EGL or OpenGL extension headers.

As of October 19 2019, it makes compilation fail on my ArchLinux
because they are not defined anymore in the headers included.

Signed-off-by: Thomas Guillem <thomas@gllm.fr>

modules/video_output/opengl/converter_vaapi.c

@@ -35,6 +35,15 @@
 #include "converter.h"
 #include "../../hw/vaapi/vlc_vaapi.h"
 
+/* From https://www.khronos.org/registry/OpenGL/extensions/OES/OES_EGL_image.txt
+ * The extension is an OpenGL ES extension but can (and usually is) available on
+ * OpenGL implementations. */
+#ifndef GL_OES_EGL_image
+#define GL_OES_EGL_image 1
+typedef void *GLeglImageOES;
+typedef void (*PFNGLEGLIMAGETARGETTEXTURE2DOESPROC)(GLenum target, GLeglImageOES image);
+#endif
+
 struct priv
 {
     VADisplay vadpy;