Paging changes to 2.1/2.2 for backward compatibilty with 3.0

Quoting Tom Hobbs from CASSANDRA-9704:

I forgot to attach a patch for the required 2.1/2.2 changes as well. Basically, when paging in 2.x, our check to see if a new page contains the same row that the previous page ended on looks for an exact cell name match. This is fine in 2.x because we will return partial rows at the end of the page (just the row marker cell). However, in 3.0, we always return full rows. While we could make some very hacky changes to 3.0 to enable returning a partial row at the end of the page, this seems like the cleanest solution.

Tyler's patch is there