Optimized simple idct for arm by Frederic 'dilb' Boulay <dilb@handhelds.org>....

Optimized simple idct for arm by Frederic 'dilb' Boulay <dilb@handhelds.org>. Currently licensed under the GPLv2, but the author allowed to license it under the LGPL, feel free to change

Originally committed as revision 2017 to svn://svn.ffmpeg.org/ffmpeg/trunk