Add -Wno-tautological-compare to the standard compile flags, if that
is accepted.  With XCode 5.5.1 -Wtautological-compare appears to come
as standard, and it generates a lot of mostly useless noise.


git-svn-id: svn://svn.valgrind.org/valgrind/trunk@14136 a5019735-40e9-0310-863c-91ae7b9d1cf9