A GC in the access check callbacks NamedSecurityCallback and IndexedSecurityCallback
violates the contract about these callbacks.

Added a EXTERNAL VMState scope around the call to FailedAccessCheckCallback to be
consistent with the other callback invocations.

BUG=v8:1952
TEST=cctest/test-api/TurnOnAccessCheckAndRecompile
Review URL: https://chromiumcodereview.appspot.com/9425048

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@10764 ce2b1a6d-e550-0410-aec6-3dcde31c8c00