patch 8.0.0621: :stag does not respect 'switchbuf'

Problem:    The ":stag" command does not respect 'switchbuf'.
Solution:   Check 'switchbuf' for tag commands that may open a new window.
            (Ingo Karkat, closes #1681)  Define macros for the return values
            of getfile().
diff --git a/src/version.c b/src/version.c
index 6e232dc..bd02b5a 100644
--- a/src/version.c
+++ b/src/version.c
@@ -765,6 +765,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    621,
+/**/
     620,
 /**/
     619,