[Bug #12628]
This patch introduce many changes.
* Introduce concept of "Block Handler (BH)" to represent
passed blocks.
* move rb_control_frame_t::flag to ep[0] (as a special local
variable). This flags represents not only frame type, but also
env flags such as escaped.
* rename `rb_block_t` to `struct rb_block`.
* Make Proc, Binding and RubyVM::Env objects wb-protected.
Check [Bug #12628] for more details.
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@55766 b2dd03c8-39d4-4d8f-98ff-823fe69b080e