console-gl: add opengl rendering helper functions

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>

ui/shader/texture-blit.vert

@@ -0,0 +1,10 @@
+
+#version 300 es
+
+in vec2  in_position;
+out vec2 ex_tex_coord;
+
+void main(void) {
+    gl_Position = vec4(in_position, 0.0, 1.0);
+    ex_tex_coord = vec2(1.0 + in_position.x, 1.0 - in_position.y) * 0.5;
+}