ImBuf: Solve re-definition warnings

The idea now is to have FFmpeg/OIIO headers listed after
the system ones. This is because FFmpeg/OIIO might define
some constants with the same name as the ones from math.h.

FFmpeg/OIIO has ifdef around defines, but math.h doesn't
check whether constants were already defined or not, which
causes some noisy warnings.

source/blender/imbuf/intern/IMB_anim.h

@@ -72,18 +72,16 @@
 #  endif /* _WIN32 || __APPLE__ */
 #endif /* WITH_QUICKTIME */
 
-#ifdef WITH_FFMPEG
-#  include <libavformat/avformat.h>
-#  include <libavcodec/avcodec.h>
-#  include <libswscale/swscale.h>
-#endif
-
 #include "IMB_imbuf_types.h"
 #include "IMB_imbuf.h"
 
 #include "IMB_allocimbuf.h"
 
-
+#ifdef WITH_FFMPEG
+#  include <libavformat/avformat.h>
+#  include <libavcodec/avcodec.h>
+#  include <libswscale/swscale.h>
+#endif
 
 /* actually hard coded endianness */
 #define GET_BIG_LONG(x) (((uchar *) (x))[0] << 24 | ((uchar *) (x))[1] << 16 | ((uchar *) (x))[2] << 8 | ((uchar *) (x))[3])

source/blender/imbuf/intern/anim_movie.c

@@ -85,22 +85,21 @@
 #include "IMB_imbuf_types.h"
 #include "IMB_imbuf.h"
 
+#include "IMB_colormanagement.h"
+#include "IMB_colormanagement_intern.h"
+
 #include "IMB_anim.h"
 #include "IMB_indexer.h"
 
 #ifdef WITH_FFMPEG
-#include <libavformat/avformat.h>
-#include <libavcodec/avcodec.h>
-#include <libavutil/rational.h>
-#include <libswscale/swscale.h>
-
-#include "ffmpeg_compat.h"
+#  include <libavformat/avformat.h>
+#  include <libavcodec/avcodec.h>
+#  include <libavutil/rational.h>
+#  include <libswscale/swscale.h>
 
+#  include "ffmpeg_compat.h"
 #endif //WITH_FFMPEG
 
-#include "IMB_colormanagement.h"
-#include "IMB_colormanagement_intern.h"
-
 int ismovie(const char *UNUSED(filepath))
 {
 	return 0;

source/blender/imbuf/intern/oiio/openimageio_api.cpp

@@ -31,11 +31,6 @@
 
 #include <set>
 
-#include <openimageio_api.h>
-#include <OpenImageIO/imageio.h>
-
-OIIO_NAMESPACE_USING
-
 #if defined(WIN32) && !defined(FREE_WINDOWS)
 #include "utfconv.h"
 #endif
@@ -53,6 +48,11 @@ extern "C"
 #include "IMB_colormanagement_intern.h"
 }
 
+#include <openimageio_api.h>
+#include <OpenImageIO/imageio.h>
+
+OIIO_NAMESPACE_USING
+
 using namespace std;
 
 typedef unsigned char uchar;