patch 9.0.0579: using freed memory when 'tagfunc' wipes out buffer

Problem:    Using freed memory when 'tagfunc' wipes out buffer that holds
            'complete'.
Solution:   Make a copy of the option.  Make sure cursor position is valid.
diff --git a/src/version.c b/src/version.c
index ff82644..1061e4c 100644
--- a/src/version.c
+++ b/src/version.c
@@ -700,6 +700,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    579,
+/**/
     578,
 /**/
     577,