lavc: Add missing mem.h header to libxvid and screenpresso

libavcodec/libxvid.c

@@ -34,6 +34,7 @@
 #include "libavutil/internal.h"
 #include "libavutil/intreadwrite.h"
 #include "libavutil/mathematics.h"
+#include "libavutil/mem.h"
 #include "libavutil/opt.h"
 
 #include "avcodec.h"

libavcodec/screenpresso.c

@@ -39,6 +39,7 @@
 
 #include "libavutil/imgutils.h"
 #include "libavutil/internal.h"
+#include "libavutil/mem.h"
 
 #include "avcodec.h"
 #include "internal.h"