Move picture-sse2.c to src/inline-optimizations/.

- Having it in the src dir even though it's not a module on it's own breaks
  the scons build script. It's probably better to have these a little bit
  separated from the normal code anyway.

src/inline-optimizations/picture-sse2.c

@@ -21,7 +21,7 @@
  * \file
  */
 
-#include "picture.h"
+#include "../picture.h"
 #include <immintrin.h>
 
 #ifdef __SSE2__

src/picture.c

@@ -770,7 +770,7 @@ static unsigned hor_sad(const pixel *pic_data, const pixel *ref_data,
 
 
 #if defined(__SSE2__)
-#include "picture-sse2.c"
+#include "inline-optimizations/picture-sse2.c"
 #elif defined(__ALTIVEC__)
 #include "picture-altivec.c"
 #else