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_mzsch.c b/src/if_mzsch.c
index 54474bd..23b67a9 100644
--- a/src/if_mzsch.c
+++ b/src/if_mzsch.c
@@ -2132,6 +2132,7 @@
 
     win->win->w_cursor.lnum = lnum;
     win->win->w_cursor.col = col;
+    win->win->w_set_curswant = TRUE;
     update_screen(VALID);
 
     raise_if_error();