Fix signed/unsigned warning, make pcapa a size_t
Fix signed/unsigned warning.
Fix signed/unsigned warning, size_t for start_index was discarded.
Add comments in mrb_get_args() func.
Merge pull request #1336 from carsonmcdonald/warnfix3

More unsigned signed warning fixes
Merge pull request #1337 from suzukaze/add-comments-in-class-c

Add comments in mrb_get_args() func.