filesystems: Add config.h inclusion

Otherwise we may forget compiling binfmt_misc_virtualized code.
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>

criu/filesystems.c

@@ -4,6 +4,7 @@
 #include <fcntl.h>
 #include <sys/mount.h>
 
+#include "config.h"
 #include "int.h"
 #include "common/compiler.h"
 #include "xmalloc.h"