Include altivec.h before any other vlc header

Including it after stdbool will cause compile failures as pointed by
Mike Frysinger in https://bugs.gentoo.org/show_bug.cgi?id=224289Signed-off-by: Rémi Denis-Courmont <rem@videolan.org>

modules/video_filter/deinterlace.c

@@ -30,16 +30,16 @@
 # include "config.h"
 #endif
 
+#ifdef HAVE_ALTIVEC_H
+#   include <altivec.h>
+#endif
+
 #include <vlc/vlc.h>
 #include <vlc_plugin.h>
 #include <vlc_vout.h>
 #include <vlc_sout.h>
 #include "vlc_filter.h"
 
-#ifdef HAVE_ALTIVEC_H
-#   include <altivec.h>
-#endif
-
 #ifdef CAN_COMPILE_MMXEXT
 #   include "mmx.h"
 #endif