patch 8.0.0847: :argadd without argument can't handle space in file name

Problem:    :argadd without argument can't handle space in file name. (Harm te
            Hennepe)
Solution:   Escape the space. (Yasuhiro Matsumoto, closes #1917)

src/version.c

@@ -769,6 +769,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    847,
 /**/
     846,
 /**/