Updates for ANGLE_multiple_render_targets

git-svn-id: http://angleproject.googlecode.com/svn/trunk@1730 736b8ea6-26fd-11df-bfd4-992fa37f6226
Document GetIntegerv errors in ANGLE_framebuffer_blit.

git-svn-id: http://angleproject.googlecode.com/svn/trunk@1731 736b8ea6-26fd-11df-bfd4-992fa37f6226