[boost] [gil] added hsl color space to gil

Hi guys, I have added the HSL color space as an extension to gil. The code is structured similar to other color spaces, like rgb. You can get the code at http://gil-contributions.googlecode.com/svn/trunk/gil_2/boost/gil/extension/... To construct a hsl view from a rgb image use the gil way: color_converted_view<hsl32f_pixel_t>( rgb_view, hsl_view ); The other way around would be: color_converted_view<rgb8_pixel_t>( hsl_view, rgb_view ); So far, there is only hsl32f_xxx_t possible. But I think that's OK for a start. Please let me know what you think. Next will be the HSV color space. Christian