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.

llvm-svn: 92889