Use A.append(...) instead of A.insert(A.end(), ...) when A is a

Use A.append(...) instead of A.insert(A.end(), ...) when A is a
SmallVector, and other SmallVector simplifications.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@106452 91177308-0d34-0410-b5e6-96231b3b80d8