Change std::deque => std::vector. No functionality change.

There is no reason to use std::deque here over std::vector. Thus given the
performance differences inbetween the two it makes sense to change deque to
vector.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@196524 91177308-0d34-0410-b5e6-96231b3b80d8