Use RARRAY_* macro instead of accessing RArray field.
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'
Allow parenthesed do-block in cmdarg

Flush cmdarg flags inside left-paren in a command argument, to allow
parenthesed `do-block` as an argument without arguments parentheses.
`CMDARG_PUSH(0)` for tLPAREN_ARG is before `CMDARG_PUSH(1)` in
`command_args` due to look-ahead.
Merge pull request #2081 from nobu/parenthesed_do-block_in_cmdarg

Allow parenthesed do-block in cmdarg
Use boolean macro instead of integer literal in `is_debug_info_defined`.
Merge pull request #2083 from take-cheeze/use_bool_macro

Use boolean macro instead of integer literal in `is_debug_info_defined`.