rename rb_execution_context_t::stack(_size) to vm_stack(_size).
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@59563 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
rename rb_execution_context_t::stack(_size) to vm_stack(_size).
VM stack. To make it clear, this fix renames
rb_execution_context_t::stack(_size) to vm_stack(_size).
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@59563 b2dd03c8-39d4-4d8f-98ff-823fe69b080e