Used pthread name functions returning result for FreeBSD and DragonFly
`pthread_getname_np` and `pthread_setname_np` received a wider adoption in past years and was added to:
* FreeBSD by June 11 2020 via [`2ef84b7da9a6c3e23b4a135e6e863581f16d46e1`](2ef84b7da9),
* DargonFly by March 8 2021 via [`ab5dc9aceb34419d1c4b6006739e61acee8ee999`](https://gitweb.dragonflybsd.org/dragonfly.git/commitdiff/ab5dc9aceb34419d1c4b6006739e61acee8ee999).
There's not so much advantage except that the result can be checked in debug builds. Ideally it should be unified with Linux' implementation, but it trims the input.