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)
diff --git a/src/version.c b/src/version.c
index 9eb8b1a..0d144bb 100644
--- a/src/version.c
+++ b/src/version.c
@@ -770,6 +770,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    847,
+/**/
     846,
 /**/
     845,