FreeBSD fix

git-svn-id: file:///var/local/repositories/mplayer/trunk/postproc@14699 b3059339-0415-0410-9bf9-f77b7e298cf2

swscale.c

@@ -53,6 +53,7 @@ untested special converters
 #include <string.h>
 #include <math.h>
 #include <stdio.h>
+#include <unistd.h>
 #include "../config.h"
 #include "../mangle.h"
 #include <assert.h>