Provide common implementation for ReadDirent based on Getdents for
aix, *bsd and linux.
Add Getdents on aix as a wrapper around getdirent.
Keep the implementation for ReadDirent based on Getdirentries for
darwin and dragonfly.
Change-Id: I09094156a1452118ba48af4f14dfe44b1ab745d3
Reviewed-on: https://go-review.googlesource.com/c/sys/+/182321
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Benny Siegert <bsiegert@gmail.com>
