Fix pg_current_logfile() to not emit a carriage return on Windows.
Due to not having our signals straight about CRLF vs. LF line
termination, the output of pg_current_logfile() included a trailing
\r on Windows. To fix, force the file descriptor it uses into text
mode.
While here, move a couple of local variable declarations to make
the function's logic clearer.
In v12 and v13, also back-patch the test added by
1c4e88e2f so that
this function has some test coverage. However, the 004_logrotate.pl
test script doesn't exist before v12, and it didn't seem worth adding
to older branches just for this.
Per report from Thomas Kellerer. Back-patch to v10 where this
function was added.
Discussion: https://postgr.es/m/
412ae8da-76bb-640f-039a-
f3513499e53d@gmx.net