* vm_insnhelper.c (argument_error): insert dummy frame to make
a backtrace object intead of modify backtrace string array.
[Bug #9295]
* test/ruby/test_backtrace.rb: add a test for this patch.
fix test to compare a result of Exception#backtrace with
a result of Exception#backtrace_locations.
merge revision(s) 44411: [Backport #9295]
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_1@44431 b2dd03c8-39d4-4d8f-98ff-823fe69b080e