title: Can we delete vertex and fragment shaders after link shader program
body: <p>As title said, Can I do this in my program:</p>
  
  <pre><code>vertex = glCreateShader(GL_VERTEX_SHADER);
  /* ... */
  fragment = glCreateShader(GL_FRAGMENT_SHADER);
  /* ... */
  program = glCreateProgram();
  glAttachShader(program, vertex);
  glAttachShader(program, fragment);
  glLinkProgram(program);
  /* All things done */
  
  glDeleteShader(vertex); /* &lt;~ Can I do this now? */
  glDeleteShader(vertex); /* &lt;~ Can I do this now? */
  
  /* And in render procedure */
  glUseProgram(program); /* &lt;~ Still use program without any problem? */
  /* ... */
  </code></pre>