Minor optimization to constant evaluation: don't bother computing expr source locations for diagnostics we're not going to emit, and don't track the subobject designator outside C++11 (since we're not going to use it anyway).
Minor optimization to constant evaluation: don't bother computing expr source
locations for diagnostics we're not going to emit, and don't track the subobject
designator outside C++11 (since we're not going to use it anyway).

This seems to give about a 0.5% speedup on 403.gcc/combine.c, but the results
were sufficiently noisy that I can't reject the null hypothesis.


git-svn-id: ffe668792ed300d6c2daa1f6eba2e0aa28d7ec6c@152761 91177308-0d34-0410-b5e6-96231b3b80d8

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