4.1.1

@veprbl added support for reading ROOT TTables: PR #418.

@jpivarski fixed the warning handling for old XRootD clients: PR #425.

@jpivarski fixed several performance bugs and one bug-bug in writing histograms and TTrees: PRs #426 and #428. See the GitHub conversations for measurements.

A quantitative rule of thumb derived from that work is that you want to call TTree.extend with no less than ~100 kB per array branch. This is roughly the same scale that would be preferred for reading TTree data (you want TBaskets to be about 100 kB or larger), but in writing, you get to control it.