patch 8.1.2182: test42 seen as binary by git diff

Problem:    Test42 seen as binary by git diff.
Solution:   Add .gitattributes file.  Make explicit that 'cpo' does not
            contain 'S'. (Daniel Hahler, closes #5072)

.gitattributes

@@ -0,0 +1 @@
+src/testdir/test42.in diff

Filelist

@@ -4,6 +4,7 @@
 # source files for all source archives
 SRC_ALL =	\
 		.gitignore \
+		.gitattributes \
 		.hgignore \
 		.lgtm.yml \
 		.travis.yml \

src/version.c

@@ -741,6 +741,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    2182,
 /**/
     2181,
 /**/