patch 8.1.0463: "simalt ~x" in .vimrc blocks swap file prompt

Problem:    "simalt ~x" in .vimrc blocks swap file prompt.
Solution:   Flush buffers before prompting. (Yasuhiro Matsumoto,
            closes #3518, closes #2192)
diff --git a/src/version.c b/src/version.c
index 103483a..90588ef 100644
--- a/src/version.c
+++ b/src/version.c
@@ -793,6 +793,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    463,
+/**/
     462,
 /**/
     461,