compile.c (iseq_set_sequence): check for multiplication overflow

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@47292 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
* 2014-08-27

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@47293 b2dd03c8-39d4-4d8f-98ff-823fe69b080e