Changes included (2 changes).

Change 0e05b04b9437bd3265478f55625078254c80bb1d by andrew hanushevsky <[log in to unmask]> (1 file): Document the enablement of sendfile() with previous patch. Note all cmake-enabled xrootd versions have *not* used sendfile until this patch. This generally results in poor performance, so this patch is essential.

Change 048718079453d293ce87e311f090ca6fdc540375 by andrew hanushevsky <[log in to unmask]> (4 files): Add sendfile definition to cmake so that sendfile actually gets compiled!