fix #7203 and #7218

[tkelman]

for Windows users who have git configured with \r\n line endings,
or modify the source in an editor that always uses \r\n

[vtjnash]

There is something slightly evil about not getting back the bytes that you tried to just write. I'm inclined to just add an assertion to the makefile that you have configured git to preserve line endings.

[Keno]

I'm in agreement with Jameson.

[JeffBezanson]

I agree with Keno and Jameson, but the rest of this test file does use $(nl) everywhere, so we might as well be consistent.

[tkelman]

I agree that we should encourage configuring git to always use unix line endings, but what about someone who installs from a binary, then modifies the test in some trivial way in a lousy editor? I think we should encourage everyone who installs a binary to immediately run the test suite as the first thing they do, but there are still several failures remaining until tests can all pass on Windows.