Updated gtest to version 1.7.0.

Fixes issue with building with new XCode 5.0
version being released later this month.

Change-Id: I3561fbe2392770f0021defdc25cc1e7779e45420
Reviewed-on: http://review.couchbase.org/28871
Reviewed-by: Trond Norbye <trond.norbye@gmail.com>
Tested-by: Brett Lawson <brett19@gmail.com>