Fix indentation in keywords
Update Travis CI build to install gperf.
Merge pull request #1037 from carsonmcdonald/traviscigperf

Update Travis CI build to install gperf
Merge pull request #1036 from kano4/pr-fix-indentation-in-keywords

Fix indentation in keywords
update lex.def
remove gperf installation that is not needed if src/lex.def is properly updated; cancel #1037
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
fix the type of value that is returned by bit-shift expression.
 fix the type of value that is returned by bit-shift expression.
"Ax" is larger than 16-bit.
fix the type of value that is returned by bit-shift expression.
fix comment.
Use `
Use mrb_intern2
Use mrb_intern2() instead of mrb_intern(). This is for avoiding overhead by strlen().
Make intern_gen() inline. This is enough tiny to be inlined.
Add an internal function intern_c(). It reduces function call parameter. For maintainability and performance.
Add new API mrb_intern_cstr(). This is for naming orthogonality. mrb_intern is also left for backward compatibility.