mruby/mruby — pull request #803 by masamitsu-murase (2013-01-30 11:57:18+00:00)
Title: Protect proc of ensure.

Protect proc of ensure from GC until `ecall` is called.

The following code causes segmentation fault in the current implementation.
```ruby
def test
begin
begin
return
ensure
puts "."
end
ensure
puts "."
end
end

while true
test
end
```

This issue was found by iij's test case.