Uproot

jpivarski fixed another Uproot-writing bug: writing TTrees didn't update the FreeSegments record, which means that writing another TTree (with another file handle, with `uproot.update` or ROOT) could overwrite the first TTree.

**Like 4.1.4, this is an important bug-fix for anyone creating a robust dataset of ROOT files.** (It doesn't affect you if you consider all files to be write-once only, but if you're ever thinking of updating files, this will matter. And besides, correctness is important in principle!)

jpivarski added TStreamerInfo for TTrees in files written by Uproot. **If you're using an older version, you're producing files without TStreamerInfo!** (Which means they won't be readable in some older versions of ROOT, and possibly not new ones, either.) PR 472.

Also corrected the TLeaf fTitle for jagged arrays, which is needed to read jagged arrays back in ROOT's `TTree::Draw` and `TTree::Scan`, but not for iteration in PyROOT (which is what we had been using for testing). PR 458.

Added an implementation of non-split TClonesArray, which makes more files readable: PR 467, and added RNTuple to the `must_be_attached` list, which enables RNTuple objects to read more data (like TTrees): PR 463. That's just a step in developing RNTuple-reading capabilities.

nsmith- fixed Awkward Forms for objects: PR 441, and implemented regular array support for TClonesArray: PR 442.

jpivarski fixed Pandas representations of leaf-lists (structs) and non-leaf-lists in the same DataFrame: PR 449. Fixed `uproot.lazy` for empty TTrees and boost-histogram with no title: 451. Fixed issue 439 by checking to see if an array is an Awkward Array before checking to see if it could be NumPy: 453. Fixed both Delphes bugs in issue 438: PR 454.

jrueb fixed `uproot.recreate` so that it immediately truncates the opened file if it exists: PR 431.

jpivarski fixed index manipulation for multi-file tuples of DataFrames: PR 432. Fixed multidimensional Float16_t interpretation: PR 434. Fixed KeyError when scanning class dependencies and a streamer of the required version does not exist in the file: PR 437.

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](https://uproot.readthedocs.io/en/latest/uproot.writing.writable.WritableTree.html#uproot-writing-writable-writabletree-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.

**The main new feature in this release is that Uproot 4 can now write ROOT files.** It is no longer necessary to use Uproot 3 for anything: Uproot 4's capabilities exceed Uproot 3's in all ways that are currently known to me.

This was implemented in PRs 405, 406, 408, 409, 412, 414, 415, 416, 420, 421, and was described in Discussion 321. All the new functions are documented, and an overview is presented in the [Getting Started Guide](https://uproot.readthedocs.io/en/latest/basic.html#opening-a-file-for-writing).

Other updates for this release:

* jpivarski removed warning when XRootD is installed but not used: PR 388.
* chrisburr allowed XRootD version strings to be non-numeric (e.g. from a self-built copy of the library): PR 395.
* bnavigator marked test 0220 with the network tag, since it uses the network: PR 396.
* jpivarski handled dimensions in a leaf-list: 399.
* jpivarski removed '' fields from lazy Forms, fixing lazy TLorentzVector: PR 403.
* klieret fixed links to source in Sphinx: PR 410.
* jpivarski allowed Float16_t to have up to 32 bits: PR 411.
* veprbl added support for reading TDatime: PR 407.