patch 8.1.0212: preferred cursor column not set in interfaces

Problem:    Preferred cursor column not set in interfaces.
Solution:   Set w_set_curswant when setting the cursor. (David Hotham,
            closes #3060)
diff --git a/src/if_lua.c b/src/if_lua.c
index c0d809a..7602c80 100644
--- a/src/if_lua.c
+++ b/src/if_lua.c
@@ -1377,6 +1377,7 @@
 	luaV_checksandbox(L);
 #endif
 	w->w_cursor.col = v - 1;
+	w->w_set_curswant = TRUE;
 	update_screen(VALID);
     }
     else if (strncmp(s, "width", 5) == 0)