use ISXDIGIT instead isxdigit on parser.y:3485
Refactor kernel.c and class.c
Merge pull request #1190 from lateau/master

tiny fix on parser.y: change isxdigit to ISXDIGIT
Merge pull request #1191 from h2so5/refactor-kernel-and-class

Refactor kernel.c and class.c
Add a test for respond_to_missing?
Add implementation for respond_to_missing?
Merge pull request #1194 from carsonmcdonald/rtomissingimpl

Implement respond_to_missing?
Module#class_variables should check superclasses
fix test to check class variables in superclasses
small consmetic fix
wrong type cast
put spaces after if/while