gl: Fix compiler warning about unused const variable with gcc 6

CC       libgstgl_x11_la-gstglcontext_glx.lo
In file included from gstglcontext_glx.c:39:0:
../utils/opengl_versions.h:52:43: error: ‘gles2_versions’ defined but not used [-Werror=unused-const-variable]
 static const struct { int major, minor; } gles2_versions[] = {
                                           ^~~~~~~~~~~~~~

gst-libs/gst/gl/Makefile.am

@@ -70,7 +70,8 @@ libgstgl_@GST_API_VERSION@include_HEADERS = \
 
 noinst_HEADERS = \
 	gstglsl_private.h \
-	utils/opengl_versions.h
+	utils/opengl_versions.h \
+	utils/gles_versions.h
 
 
 libgstgl_@GST_API_VERSION@_la_LIBADD = \

gst-libs/gst/gl/egl/gstglcontext_egl.c

@@ -31,6 +31,7 @@
 #include "gstglcontext_egl.h"
 #include <gst/gl/egl/gstegl.h>
 #include "../utils/opengl_versions.h"
+#include "../utils/gles_versions.h"
 
 #if GST_GL_HAVE_WINDOW_X11
 #include "../x11/gstglwindow_x11.h"

gst-libs/gst/gl/utils/gles_versions.h

@@ -0,0 +1,38 @@
+/*
+ * GStreamer
+ * Copyright (C) 2015 Matthew Waters <matthew@centricular.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.
+ */
+
+#ifndef _GLES_VERSIONS_H_
+#define _GLES_VERSIONS_H_
+
+/* list of known OpenGL versions */
+/* *INDENT-OFF* */
+
+static const struct { int major, minor; } gles2_versions[] = {
+   {3, 2},
+   {3, 1},
+   {3, 0},
+
+   {2, 0},
+
+   {0, 0} /* end of list */
+};
+/* *INDENT-ON* */
+
+#endif /* _GLES_VERSIONS_H_ */

gst-libs/gst/gl/utils/opengl_versions.h

@@ -49,15 +49,6 @@ static const struct { int major, minor; } opengl_versions[] = {
    {0, 0} /* end of list */
 };
 
-static const struct { int major, minor; } gles2_versions[] = {
-   {3, 2},
-   {3, 1},
-   {3, 0},
-
-   {2, 0},
-
-   {0, 0} /* end of list */
-};
 /* *INDENT-ON* */
 
 #endif /* _OPENGL_VERSIONS_H_ */