Some warning cleanups

A trivial one in source/blender/render/intern/source/ray.c

----------------------------------------------------------
--- ray.c_orig  2004-04-29 13:38:04.000000000 +0000
+++ ray.c       2004-04-29 13:38:09.000000000 +0000
@@ -1033,7 +1033,7 @@ static int d3dda(Isect *is)
        int ocx1,ocx2,ocy1, ocy2,ocz1,ocz2;

        /* clip with octree */
-       if(branchcount==0) return NULL;
+       if(branchcount==0) return 0;

        /* do this before intersect calls */
        raycount++;
----------------------------------------------------------

Implicit declaration of swab in Linux, needs to define __USE_XOPEN at
source/blender/src:

---------------------------------------------------------
--- editsound.c_orig    2004-04-29 14:42:00.000000000 +0000
+++ editsound.c 2004-04-29 14:47:32.000000000 +0000
@@ -40,7 +40,9 @@
 #endif

 #ifndef WIN32
+#define __USE_XOPEN /* We need this for swab */
 #include <unistd.h>
+#undef __USE_XOPEN
 #else
 #include <io.h>
 #endif
---------------------------------------------------------

---------------------------------------------------------
--- seqaudio.c_orig     2004-04-29 14:43:12.000000000 +0000
+++ seqaudio.c  2004-04-29 14:47:46.000000000 +0000
@@ -33,7 +33,9 @@
 #include <string.h>

 #ifndef WIN32
+#define __USE_XOPEN /* We need this for swab */
 #include <unistd.h>
+#undef __USE_XOPEN
 #else
 #include <io.h>
 #include "BLI_winstuff.h"
---------------------------------------------------------
        Panagiotis Papadakos