-Wunsequenced: if the LHS of an &&, || or ?: is not constant, check for
unsequenced operations in the RHS. We don't compare the RHS with the rest of
the expression yet; such checks will need care to avoid diagnosing unsequenced
operations which are both in conditionally-evaluated subexpressions which
actually can't occur together, such as in '(b && ++x) + (!b && ++x)'.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@172760 91177308-0d34-0410-b5e6-96231b3b80d8