Makefile: propagate NATIVE_CRLF to C

Commit 95f31e9a (convert: The native line-ending is \r\n on MinGW,
2010-09-04) correctly points out that the NATIVE_CRLF setting is
incorrectly set on Mingw git. However, the Makefile variable is not
propagated to the C preprocessor and results in no change. This patch
pushes the definition to the C code and adds a test to validate that
when core.eol as native is crlf, we actually normalize text files to
this line ending convention when core.autocrlf is false.

Signed-off-by: Pat Thoyts <patthoyts@users.sourceforge.net>
Signed-off-by: Stepan Kasal <kasal@ucw.cz>
Signed-off-by: Torsten Bögershausen <tboegi@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
MinGW: update tests to handle a native eol of crlf

Some of the tests were written with the assumption that the native
eol would always be lf. After defining NATIVE_CRLF on MinGW, these
tests began failing.  This change will update the tests to also
handle a native eol of crlf.

Signed-off-by: Brice Lambson <bricelam@live.com>
Helped-by: Eric Sunshine <sunshine@sunshineco.com>
Signed-off-by: Torsten Bögershausen <tboegi@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>