Add a Java API for OpenGL ES 2.0.

Currently this API is hidden.

Add a test program.
diff --git a/opengl/tools/glgen/src/GenerateGLES.java b/opengl/tools/glgen/src/GenerateGLES.java
index 60775b7..08063f3 100644
--- a/opengl/tools/glgen/src/GenerateGLES.java
+++ b/opengl/tools/glgen/src/GenerateGLES.java
@@ -70,7 +70,7 @@
 
         // Generate files
         for(String suffix: new String[] {"GLES10", "GLES10Ext",
-                "GLES11", "GLES11Ext"})
+                "GLES11", "GLES11Ext", "GLES20"})
         {
             BufferedReader spec11Reader =
                 new BufferedReader(new FileReader("specs/gles11/"