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)

runtime/doc/eval.txt

@@ -2412,6 +2412,8 @@ sign_define({name} [, {dict}])	Number	define or update a sign
 sign_getdefined([{name}])	List	get a list of defined signs
 sign_getplaced([{expr} [, {dict}]])
 				List	get a list of placed signs
+sign_jump({id}, {group}, {expr})
+				Number	jump to a sign
 sign_place({id}, {group}, {name}, {expr} [, {dict}])
 				Number	place a sign
 sign_undefine([{name}])		Number	undefine a sign
@@ -7997,6 +7999,21 @@ sign_getplaced([{expr} [, {dict}]])			*sign_getplaced()*
 
 			" Get a List of all the placed signs
 			echo sign_getplaced()
+<
+							*sign_jump()*
+sign_jump({id}, {group}, {expr})
+		Open the buffer {expr} or jump to the window that contains
+		{expr} and position the cursor at sign {id} in group {group}.
+		This is similar to the |:sign-jump| command.
+
+		For the use of {expr}, see |bufname()|.
+
+		Returns the line number of the sign. Returns -1 if the
+		arguments are invalid.
+
+		Example: >
+			" Jump to sign 10 in the current buffer
+			call sign_jump(10, '', '')
 <
 							*sign_place()*
 sign_place({id}, {group}, {name}, {expr} [, {dict}])

runtime/doc/sign.txt

@@ -263,13 +263,13 @@ See |sign_unplace()| for the equivalent Vim script function.
 		all the files it appears in.
 
 :sign unplace *
-		Remove placed signs in the global group from all the files.
+		Remove all placed signs in the global group from all the files.
 
 :sign unplace * group={group}
-		Remove placed signs in group {group} from all the files.
+		Remove all placed signs in group {group} from all the files.
 
 :sign unplace * group=*
-		Remove placed signs in all the groups from all the files.
+		Remove all placed signs in all the groups from all the files.
 
 :sign unplace
 		Remove a placed sign at the cursor position. If multiple signs
@@ -317,6 +317,8 @@ See |sign_getplaced()| for the equivalent Vim script function.
 
 JUMPING TO A SIGN					*:sign-jump* *E157*
 
+See |sign_jump()| for the equivalent Vim script function.
+
 :sign jump {id} file={fname}
 		Open the file {fname} or jump to the window that contains
 		{fname} and position the cursor at sign {id}.

runtime/doc/usr_41.txt

@@ -987,6 +987,7 @@ Signs:						*sign-functions*
 	sign_define()		define or update a sign
 	sign_getdefined()	get a list of defined signs
 	sign_getplaced()	get a list of placed signs
+	sign_jump()		jump to a sign
 	sign_place()		place a sign
 	sign_undefine()		undefine a sign
 	sign_unplace()		unplace a sign