Improve HConstant::ImmortalImmovable() to check for all immortal immovable roots.

Move the list to IMMORTAL_IMMOVABLE_ROOT_LIST in heap.h, and
automatically include INTERNALIZED_STRING_LIST and STRING_TYPE_LIST.

R=hpayer@chromium.org, mstarzinger@chromium.org

Review URL: https://codereview.chromium.org/146623003

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@18970 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Fixed a few lifetime/ownership issues in cctest/test-api.

   * Fixed CompileExternalTwoByteSource: Registered resources should
     better still be alive when they are accessed.

   * Fixed ownership in cctest/test-api/VisitExternalStrings.

R=ulan@chromium.org

Review URL: https://codereview.chromium.org/139923003

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@18971 ce2b1a6d-e550-0410-aec6-3dcde31c8c00