patch 9.0.0581: adding a character for incsearch fails at end of line

Problem:    Adding a character for incsearch fails at end of line.
Solution:   Only check cursor line number.
diff --git a/src/version.c b/src/version.c
index eb6ad87..0acc0d4 100644
--- a/src/version.c
+++ b/src/version.c
@@ -700,6 +700,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    581,
+/**/
     580,
 /**/
     579,