add lava GLSL program and render lava floor

assets/fs/shaders/lava.f.glsl

@@ -0,0 +1,9 @@
+
+uniform sampler2D tex;
+
+varying vec2 tex_coord_i;
+
+void main(void)
+{
+    gl_FragColor = texture2D(tex, tex_coord_i);
+}

assets/fs/shaders/lava.v.glsl

@@ -0,0 +1,14 @@
+
+uniform mat4 projection;
+uniform mat4 modelview;
+
+attribute vec3 pos;
+attribute vec2 tex_coord;
+
+varying vec2 tex_coord_i;
+
+void main(void)
+{
+    gl_Position = projection * modelview * vec4(pos, 1);
+    tex_coord_i = tex_coord;
+}