vm_backtrace.c: initialize flag
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@44699 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
vm_backtrace.c: initialize flag
header-printed flag.
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@44699 b2dd03c8-39d4-4d8f-98ff-823fe69b080e