Replace mrb_intern() func with mrb_intern2() func or mrb_intern_cstr() func.
Refactor codes using REGEXP_CLASS define.
2.Replace mrb_intern() func with mrb_intern2() func or mrb_intern_cstr() func.
Merge pull request #1364 from suzukaze/refactor-in-mrb-intern

Replace mrb_intern() func with mrb_intern2() or mrb_intern_cstr() func.
Merge pull request #1365 from suzukaze/refactor-using-REGEXP_CLASS

Refactor codes using REGEXP_CLASS define.
add the name 'Narihiro Nakamura'
Merge pull request #1366 from authorNari/patch-1

add the name 'Narihiro Nakamura'