* proc.c: add Binding#local_variable_get/set/defined?
  to access local variables which a binding contains.
  Most part of implementation by nobu.
* test/ruby/test_proc.rb: add a tests for above.
* vm.c, vm_core.h (rb_binding_add_dynavars): add a new function
  to add a new environment to create space for new local variables.



git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@42464 b2dd03c8-39d4-4d8f-98ff-823fe69b080e