compile.c: zero fill
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@63098 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
compile.c: zero fill
resizing only, not to leave garbages.
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@63098 b2dd03c8-39d4-4d8f-98ff-823fe69b080e