Mark .bat files as requiring CR/LF endings

Just like the natural line ending for Unix shell scripts consist of a
single Line Feed, the natural line ending for (DOS) Batch scripts
consists of a Carriage Return followed by a Line Feed.

It seems that both Unix shell script interpreters and the interpreter
for Batch scripts (`cmd.exe`) are keen on seeing the "right" line
endings.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

.gitattributes

@@ -5,6 +5,7 @@
 *.pl eof=lf diff=perl
 *.pm eol=lf diff=perl
 *.py eol=lf diff=python
+*.bat eol=crlf
 /Documentation/**/*.txt eol=lf
 /command-list.txt eol=lf
 /GIT-VERSION-GEN eol=lf