t4256: mark support files as LF-only

The test t4256-am-format-flowed.sh requires carefully applying a
patch after ignoring padding whitespace. This breaks if the file
is munged to include CRLF line endings instead of LF.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>

Author: dscho

t/.gitattributes

@@ -16,6 +16,7 @@ t[0-9][0-9][0-9][0-9]/* -whitespace
 /t4135/* eol=lf
 /t4211/* eol=lf
 /t4252/* eol=lf
+/t4256/1/* eol=lf
 /t5100/* eol=lf
 /t5515/* eol=lf
 /t556x_common eol=lf