Move the local includes below the system includes

This fixes a compilation issue on OS X 10.4, where some system headers were
included implicitly through dsputil_altivec.h (with _POSIX_C_SOURCE defined),
and other system headers included later, with _POSIX_C_SOURCE undefined at
that time.

Originally committed as revision 22327 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/ppc/check_altivec.c

@@ -22,9 +22,6 @@
  * Checks for AltiVec presence.
  */
 
-#include "config.h"
-#include "dsputil_altivec.h"
-
 #ifdef __APPLE__
 #undef _POSIX_C_SOURCE
 #include <sys/sysctl.h>
@@ -38,6 +35,9 @@
 #include <proto/exec.h>
 #endif /* __APPLE__ */
 
+#include "config.h"
+#include "dsputil_altivec.h"
+
 /**
  * This function MAY rely on signal() or fork() in order to make sure AltiVec
  * is present.