Support the #extension GL_ARB_draw_instanced.

Signed-off-by: ZhiqianXia <xzq0528@outlook.com>

Test/GL_ARB_draw_instanced.vert

@@ -0,0 +1,18 @@
+#version 150
+#extension GL_ARB_draw_instanced : require
+#define ID gl_InstanceID
+
+uniform mat4 gtf_ModelViewProjectionMatrix;
+uniform vec3 instanceOffsets[3];
+in vec4 va[gl_MaxVertexAttribs];
+out vec4 color;
+
+void main (void)
+{
+        vec4 vertex = vec4(va[0].xy / 3.0, va[0].zw) + vec4(instanceOffsets[ID], 1.0);
+        color = vec4(0, 0, 0, 0);
+        for (int i = 1; i < gl_MaxVertexAttribs; i++)
+                color += va[i];
+        gl_Position = gtf_ModelViewProjectionMatrix * vertex;
+        gl_PointSize = 1.0;
+}