Fix handling of core.eol=native and of crlf attribute
EolStreamTypeUtil didn't handle these correctly on Windows.
Add three new tests to verify that the crlf attribute is handled as
described at [1], and that core.eol=native produces the expected
line endings on check-out.
[1] https://git-scm.com/docs/gitattributes
Bug: 497290
Change-Id: Idd9b435e3256c1e3251cc7b966f2f0460e787f07 Signed-off-by: Thomas Wolf <thomas.wolf@paranor.ch> Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>