gl-renderer: always enable unpack subimage and RG textures in ES3 contexts

The GL_EXT_unpack_subimage and GL_EXT_texture_rg are part of the core ES
3.0 specification, so also check the GL driver version in addition to
the extension string to determine if those features are supported.

This allows using those extensions on some GL drivers that do not expose
them in the extensions string, but still support OpenGLES3.

Signed-off-by: Arnaud Vrac <avrac@freebox.fr>
Reviewed-by: Derek Foreman <derekf@osg.samsung.com>
Reviewed-by: Daniel Stone <daniels@collabora.com>

libweston/gl-renderer.c

@@ -3685,10 +3685,12 @@ gl_renderer_setup(struct weston_compositor *ec, EGLSurface egl_surface)
 	else
 		ec->read_format = PIXMAN_a8b8g8r8;
 
-	if (weston_check_egl_extension(extensions, "GL_EXT_unpack_subimage"))
+	if (gr->gl_version >= GR_GL_VERSION(3, 0) ||
+	    weston_check_egl_extension(extensions, "GL_EXT_unpack_subimage"))
 		gr->has_unpack_subimage = 1;
 
-	if (weston_check_egl_extension(extensions, "GL_EXT_texture_rg"))
+	if (gr->gl_version >= GR_GL_VERSION(3, 0) ||
+	    weston_check_egl_extension(extensions, "GL_EXT_texture_rg"))
 		gr->has_gl_texture_rg = 1;
 
 	if (weston_check_egl_extension(extensions, "GL_OES_EGL_image_external"))