X87:  ReceiverCheckMode needs to be utilized further.

port r24704.

original commit message:

  ReceiverCheckMode needs to be utilized further.

  The parameter wasn't being passed appropriately, and there was an extra
   opportunity to use mode RECEIVER_IS_STRING in SubStringStub.

BUG=
R=weiliang.lin@intel.com

Review URL: https://codereview.chromium.org/664973002

Patch from Chunyang Dai <chunyang.dai@intel.com>.

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@24714 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Revert "Enable libstdc++ debug mode in debug builds.".

This reverts commit r24676 to see if it was the cause for the mysterious
crashes on some bots. If not, we'll reland it.

TBR=svenpanne@chromium.org

Review URL: https://codereview.chromium.org/663013002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@24715 ce2b1a6d-e550-0410-aec6-3dcde31c8c00