[PATCH, GCC 4.9 branch] Fix compile time regression caused by fix to PR64111

[Caroline Tice]

Here is my promised backport to the GCC 4.9 branch, for the patch below
that went into ToT last week.  As with the previous patch, I've
verified that it fixes the problem, bootstraps and has no new
regression test failures.  Is this ok to commit to the gcc-4_9-branch?

-- Caroline Tice
cmt...@google.com

gcc/ChangeLog:

 2015-10-26  Caroline Tice  <cmt...@google.com>

        (from Richard Biener)
         * tree.c (int_cst_hash_hash):  Replace XORs with more efficient
         calls to iterative_hash_host_wide_int.

gcc-fsf-4_9.patch
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