Add multiple color buffer attachments points to gl::Framebuffer. Also addded the checks for framebuffer completeness as defined by the ES2 spec and EXT_draw_buffers. TRAC #22656 Signed-off-by: Nicolas Capens Signed-off-by: Shannon Woods Author: Jamie Madill git-svn-id: https://angleproject.googlecode.com/svn/branches/es3proto@2065 736b8ea6-26fd-11df-bfd4-992fa37f6226