Make EmplaceRow forward to AddRow (#235)
Make EmplaceRow forward to AddRow (#235)

(I think) EmplaceRow exists as a convenience for users who have values
but no row yet. Logically users are adding a row, but since they only
have values, we'll construct the Row for them. Therefore, it may make
sense to have EmplaceRow() be a simple 1-line forwarder to AddRow(), to
have a implementation for both functions.

This also simplifies the implementation a little since Row already handles all the variadic stuff.

Modulo an extra move here or there, I don't think this will result in
any extra/unnecessary copies, so I think performance wise this would be
pretty close to a wash. But someone with a better eye than me may be
able to point out if/where my assumptions are wrong.

I'm not wedded to this. It's just something for us to consider.
googleapis/google-cloud-cpp-spanner,googleapis/google-cloud-cpp-spanner,googleapis/google-cloud-cpp-spanner,googleapis/google-cloud-cpp-spanner