Fix path of `error.h`.
MODIFY
mrbgems/mruby-pack/src/pack.c
mrbgems/mruby-pack/src/pack.c
*/
#include "mruby.h"
-#include "error.h"
+#include "mruby/error.h"
#include "mruby/array.h"
#include "mruby/class.h"
#include "mruby/numeric.h"

MODIFY
mrbgems/mruby-socket/src/socket.c
mrbgems/mruby-socket/src/socket.c
#include "mruby/numeric.h"
#include "mruby/string.h"
#include "mruby/variable.h"
-#include "error.h"
+#include "mruby/error.h"
#include "mruby/ext/io.h"

Fix path of `error.h`.