It is part of GL_EXT_color_buffer_half_float.

Change-Id: Icaba1efed8b4e5ad97e583ebdad7b777cf4c7ad8
Reviewed-on: https://swiftshader-review.googlesource.com/5596Reviewed-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Nicolas Capens <capn@google.com>
Tested-by: Nicolas Capens <capn@google.com>