bugfix escape charactor for Regexp class
Backtick operation
Merge pull request #1038 from kouki-o-iij/pr-regexp-escape

bugfix escape charactor for Regexp class
Use `
Use mrb_intern2
Merge pull request #1040 from mattn/backtick

xquote operator
allow backtick as a symbol
add mrbgems/ext/mruby-numeric, and method: Integer#chr
Merge branch 'master' of github.com:kouki-o-iij/mruby