patch 8.1.0166: using dict_add_nr_str() is clumsy

Problem:    Using dict_add_nr_str() is clumsy.
Solution:   Split into two functions. (Ozaki Kiichi, closes #3154)
diff --git a/src/option.c b/src/option.c
index 504b92a..0cfc39c 100644
--- a/src/option.c
+++ b/src/option.c
@@ -13222,11 +13222,11 @@
 	    if (varp != NULL)
 	    {
 		if (opt->flags & P_STRING)
-		    dict_add_nr_str(d, opt->fullname, 0L, *(char_u **)varp);
+		    dict_add_string(d, opt->fullname, *(char_u **)varp);
 		else if (opt->flags & P_NUM)
-		    dict_add_nr_str(d, opt->fullname, *(long *)varp, NULL);
+		    dict_add_number(d, opt->fullname, *(long *)varp);
 		else
-		    dict_add_nr_str(d, opt->fullname, *(int *)varp, NULL);
+		    dict_add_number(d, opt->fullname, *(int *)varp);
 	    }
 	}
     }