[CI Stabilization] Fixed iOS build.

  * Added a method to force mGLFrameBufferID in MOAIFrameBuffer (SetGLFrameBufferID).
  * Added a method to AKU-iphone that uses SetGLFrameBufferID to force the framebuffer (AKUSetFrameBuffer)
  * Fixed iOS MoaiSample host to use AKUSetFrameBuffer instead of AKUSetDefaultFrameBuffer.
[CI Stabilization] Fixed libmoai build.
Merge git://github.com/moai/moai-dev into grayscale_image