Multi-threaded frame calculation for movie clip proxies

This commit implements multi-threaded calculation of frames
when building proxies. Both scaling and undistortion steps
are now threaded.

Frames and proxy resolution are still handled one-by-one,
saving files after every single step. So if HDD is not so
fast, this commit could have not so much benefit.

Internal changes:

- Added IMB_scaleImBuf_threaded which scales given image
  buffer in multiple threads and uses bilinear filtering.

- libmv's camera intrinsics now have SetThreads() method
  which is used to specify how many OpenMP threads to use
  for buffer distortion/undistortion.

  And yeah, this code is using OpenMP for threading.

- Reshuffled a bit libmv-capi calls and added function
  BKE_tracking_distortion_set_threads to specify number
  of threads used by intrinscis.

1 files changed, 1 insertions, 1 deletions

diff --git a/source/blender/blenkernel/intern/movieclip.c b/source/blender/blenkernel/intern/movieclip.c
index ab42d86152d..1ad0bf1988c 100644
--- a/source/blender/blenkernel/intern/movieclip.c
+++ b/source/blender/blenkernel/intern/movieclip.c
@@ -1244,7 +1244,7 @@ static void movieclip_build_proxy_ibuf(MovieClip *clip, ImBuf *ibuf, int cfra, i
 
 	scaleibuf = IMB_dupImBuf(ibuf);
 
-	IMB_scaleImBuf(scaleibuf, (short)rectx, (short)recty);
+	IMB_scaleImBuf_threaded(scaleibuf, (short)rectx, (short)recty);
 
 	quality = clip->proxy.quality;
 	scaleibuf->ftype = JPG | quality;