[IMP] add bench/bench.c

[LuoZijun]

make bench test code is clean then test_yuv_rgb.c.

DONE

1. ffmpeg_rgb24_to_yuv420p
2. ffmpeg_yuv420p_to_rgb24
3. std_rgb24_to_yuv420p

UNDONE

1. ipp_yuv420p_to_rgb24
2. ipp_rgb24_to_yuv420p
3. std_yuv420p_to_rgb24
4. duration calculations code.

and as your wish, the code indentations all with tabulations (hehe).

the undone things, i will add later.

[descampsa]

Hey,

This is interesting and seems to be well done, but frankly, i am not sure i will merge it in my repository, even when it is completed, because i want to keep the dependencies to ffmpeg as optionnal as possible, since it can be a PITA, with its continuously changing api, and all the different versions in use.

Actually, i was planning to make ffmpeg dependency completely optionnal (similarly to IPP)

I could probably use your load/save functions, to support more image formats when ffmpeg is enabled, however.

[LuoZijun]

that's ok, and i agree make ffmpeg is one option.