Fixed illegal memory operation on mruby debugger.

mrbgems/mruby-bin-debugger/tools/mrdb/apiprint.c

@@ -21,7 +21,7 @@ mrdb_check_syntax(mrb_state *mrb, mrb_debug_context *dbg, const char *expr, size
   c = mrbc_context_new(mrb);
   c->no_exec = TRUE;
   c->capture_errors = TRUE;
-  c->filename = (char*)dbg->prvfile;
+  mrbc_filename(mrb, c, (const char*)dbg->prvfile);
   c->lineno = dbg->prvline;
 
   /* Load program */