Rename CONFIG_DARWIN to SYS_DARWIN, it is not configurable (in FFmpeg).

git-svn-id: file:///var/local/repositories/mplayer/trunk/libswscale@24121 b3059339-0415-0410-9bf9-f77b7e298cf2

swscale_altivec_template.c

@@ -21,7 +21,7 @@
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
 
-#ifdef CONFIG_DARWIN
+#ifdef SYS_DARWIN
 #define AVV(x...) (x)
 #else
 #define AVV(x...) {x}

swscale_internal.h

@@ -27,7 +27,7 @@
 
 #include "avutil.h"
 
-#ifdef CONFIG_DARWIN
+#ifdef SYS_DARWIN
 #define AVV(x...) (x)
 #else
 #define AVV(x...) {x}