Mark vector::operator[] and front/back as noexcept. We already do this for string and string_view. This should give better codegen inside of noexcept functions. Add tests for op[]/front/back/at, because apparently we had none.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@356224 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed