compatibility support (mruby/mruby, iij/mruby and 1.0.0)

- refs https://github.com/mruby/mruby/commit/36e234aa377d50d8ee425c7868e0651cf78e85cf

src/file.c

@@ -8,7 +8,12 @@
 #include "mruby/class.h"
 #include "mruby/data.h"
 #include "mruby/string.h"
+
+#if MRUBY_RELEASE_NO < 10000
 #include "error.h"
+#else
+#include "mruby/error.h"
+#endif
 
 #include <sys/file.h>
 #include <fcntl.h>

src/file_test.c

@@ -8,7 +8,12 @@
 #include "mruby/class.h"
 #include "mruby/data.h"
 #include "mruby/string.h"
+
+#if MRUBY_RELEASE_NO < 10000
 #include "error.h"
+#else
+#include "mruby/error.h"
+#endif
 
 #include <sys/file.h>
 #include <libgen.h>

src/io.c

@@ -12,7 +12,12 @@
 #include "mruby/string.h"
 #include "mruby/variable.h"
 #include "mruby/ext/io.h"
+
+#if MRUBY_RELEASE_NO < 10000
 #include "error.h"
+#else
+#include "mruby/error.h"
+#endif
 
 static int mrb_io_modestr_to_flags(mrb_state *mrb, const char *modestr);
 static int mrb_io_modenum_to_flags(mrb_state *mrb, int modenum);