patch 8.1.1995: more functions can be used as methods

Problem:    More functions can be used as methods.
Solution:   Make sign functions usable as a method.
diff --git a/src/evalfunc.c b/src/evalfunc.c
index f302df7..2949c89 100644
--- a/src/evalfunc.c
+++ b/src/evalfunc.c
@@ -736,15 +736,15 @@
     {"shellescape",	1, 2, 0,	  f_shellescape},
     {"shiftwidth",	0, 1, 0,	  f_shiftwidth},
 #ifdef FEAT_SIGNS
-    {"sign_define",	1, 2, 0,	  f_sign_define},
-    {"sign_getdefined",	0, 1, 0,	  f_sign_getdefined},
-    {"sign_getplaced",	0, 2, 0,	  f_sign_getplaced},
-    {"sign_jump",	3, 3, 0,	  f_sign_jump},
-    {"sign_place",	4, 5, 0,	  f_sign_place},
-    {"sign_placelist",	1, 1, 0,	  f_sign_placelist},
-    {"sign_undefine",	0, 1, 0,	  f_sign_undefine},
-    {"sign_unplace",	1, 2, 0,	  f_sign_unplace},
-    {"sign_unplacelist",	1, 2, 0,	  f_sign_unplacelist},
+    {"sign_define",	1, 2, FEARG_1,	  f_sign_define},
+    {"sign_getdefined",	0, 1, FEARG_1,	  f_sign_getdefined},
+    {"sign_getplaced",	0, 2, FEARG_1,	  f_sign_getplaced},
+    {"sign_jump",	3, 3, FEARG_1,	  f_sign_jump},
+    {"sign_place",	4, 5, FEARG_1,	  f_sign_place},
+    {"sign_placelist",	1, 1, FEARG_1,	  f_sign_placelist},
+    {"sign_undefine",	0, 1, FEARG_1,	  f_sign_undefine},
+    {"sign_unplace",	1, 2, FEARG_1,	  f_sign_unplace},
+    {"sign_unplacelist", 1, 2, FEARG_1,	  f_sign_unplacelist},
 #endif
     {"simplify",	1, 1, 0,	  f_simplify},
 #ifdef FEAT_FLOAT