Do it all at once in preparation for Go 1.18 support.
To make this commit, I've simply modified the `fmt-check` Makefile
target to rewrite files instead of listing the differences. So this is a
fully mechanical change, it should not have introduced any errors.
It's wafer-thin :-)
Includes smoke test from upstream.
TODO: once t.TempDir is implemented, add io/fs to the list of standard library tests to run; that's a better test.
readdir is disabled on linux for 386 and arm until syscall.seek is implemented there.
windows is hard, so leaving that for later.
File src/os/dir_other_go115.go can be deleted when we drop support for go 1.15.
Also adds TestReadNonDir, which was helpful while debugging.
Ayke van Laethem
Dan Kegel
Ron Evans
Federico G. Schwindt
sago35
Takeshi Yoneda