mruby/mruby — pull request #359 by masamitsu-murase (2012-07-09 16:50:00+00:00)
Title: Add ary_modify to prevent corrupting shared array.

If 'clear' or 'delete_at' is called by shared array, segmentation fault occurs,
because 'ary_modify' is not called.

Example:
```ruby
a = [ "a", "b", "c", "d", "e", "f" ]
b = a.slice(1, 3)

a.clear
b.clear
```