fix a globalopt crash on 'bullet' (handling evaluation of a store

fix a globalopt crash on 'bullet' (handling evaluation of a store
to an element of a vector in a static ctor) which occurs with an
unrelated patch I'm testing.  Annoyingly, EvaluateStoreInto basically
does exactly the same stuff as InsertElement constant folding, but it
now handles vectors, and you can't insertelement into a vector.  It
would be 'really nice' if GEP into a vector were not legal.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@92889 91177308-0d34-0410-b5e6-96231b3b80d8