contrib: add win32 credential-helper

Since the Windows port of Git expects binary pipes, we need to make
sure the helper-end also sets up binary pipes.

Side-step CRLF-issue in test to make it pass.

Signed-off-by: Erik Faye-Lund <kusmabite@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/lib-credential.sh

@@ -18,6 +18,10 @@ check() {
 		cat stderr &&
 		false
 	fi &&
+	if test_have_prereq MINGW
+	then
+		dos2unix -q stderr
+	fi &&
 	test_cmp expect-stdout stdout &&
 	test_cmp expect-stderr stderr
 }