Change range_check before mrb_obj_alloc.
Reduce filename table creation in irep dumping to once.
Reduce children filenames listing.
It is executed per each debug filenames in irep to same ireps(children).
remove unnecessary assignment; ref #2301
git push origin masterMerge branch 'take-cheeze-refactor_dump'
Merge pull request #2282 from yui-knk/check-before-malloc

Change range_check before mrb_obj_alloc.
Merge branch 'master' of github.com:mruby/mruby