Tests that the GC doesn't mistake non-pointer constant pool entries as pointers.

Adds a test for ConstantPoolArray to ensure that the GC
doesn't mistake non-pointer entries as pointers and try
to modify them during scavenge operations.

Also adds asserts to ConstantPoolArray::set(int, *Object) to
ensure we don't add new-space pointers in constant pool
array.

R=hpayer@chromium.org

Review URL: https://codereview.chromium.org/396803009

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@22608 ce2b1a6d-e550-0410-aec6-3dcde31c8c00