patch 8.1.0717: there is no function for the ":sign jump" command

Problem:    There is no function for the ":sign jump" command.
Solution:   Add the sign_jump() function. (Yegappan Lakshmanan, closes #3780)
diff --git a/src/version.c b/src/version.c
index 9fffc2a..9d534c7 100644
--- a/src/version.c
+++ b/src/version.c
@@ -800,6 +800,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    717,
+/**/
     716,
 /**/
     715,