Implement String#index, fixes #2073
Handle utf-8 code in index/rindex
Cosmetic change
Merge pull request #2074 from mattn/fix_string_utf8_index

Implement String#index, fixes #2073
mruby-string-utf8: String#reverse! may leak memory when mrb_str_modify() raises exception
Implement String#ord, String#split for mruby-string-utf8
Merge pull request #2075 from mattn/utf8-string-ord

Implement String#ord, String#split for mruby-string-utf8
Add test for String#ord, String#split for mruby-string-utf8
Add one more test
Add a block argument with Array#uniq_bang
Add a block argument with Array#uniq
Use RARRAY_* macro instead of accessing RArray field.
mruby-string-utf8: str_subseq takes UTF-8 index, not byte index; ref #2076
mruby-string-utf8: update UTF-8 tests; ref #2076
Merge pull request #2078 from suzukaze/add-block-with-array.uniq_bang

Add block argument with Array#uniq! and Array#uniq
Add tests for utf8-string#rindex
Merge pull request #2077 from take-cheeze/rstruct_macro

Use RARRAY_* macro instead of accessing RArray field.
Merge pull request #2079 from suzukaze/add-test-of-utf8-string.rindex

Add tests for String#rindex of mruby-string-utf8.
Sort out the variables which belongs to 'mrb_callinfo' to improve 'cipush' performance.
Merge pull request #2080 from crimsonwoods/replace_disordered_callinfo_variables

Sort out the variables which belongs to 'mrb_callinfo'