patch 8.1.1682: placing a larger number of signs is slow

Problem:    Placing a larger number of signs is slow.
Solution:   Add functions for dealing with a list of signs. (Yegappan
            Lakshmanan, closes #4636)
diff --git a/src/proto/sign.pro b/src/proto/sign.pro
index 51aa0bb..50b74aa 100644
--- a/src/proto/sign.pro
+++ b/src/proto/sign.pro
@@ -22,6 +22,8 @@
 void f_sign_getplaced(typval_T *argvars, typval_T *rettv);
 void f_sign_jump(typval_T *argvars, typval_T *rettv);
 void f_sign_place(typval_T *argvars, typval_T *rettv);
+void f_sign_placelist(typval_T *argvars, typval_T *rettv);
 void f_sign_undefine(typval_T *argvars, typval_T *rettv);
 void f_sign_unplace(typval_T *argvars, typval_T *rettv);
+void f_sign_unplacelist(typval_T *argvars, typval_T *rettv);
 /* vim: set ft=c : */