patch 9.0.0734: cursor position invalid when scrolling with 'smoothscroll'

Problem:    Cursor position invalid when scrolling with 'smoothscroll' set.
            (Ernie Rael)
Solution:   Add w_valid_skipcol and clear flags when it changes.  Adjust
            w_skipcol after moving the cursor.

src/normal.c

@@ -2448,6 +2448,7 @@ nv_screengo(oparg_T *oap, int dir, long dist)
 
     if (atend)
 	curwin->w_curswant = MAXCOL;	    // stick in the last column
+    adjust_skipcol();
 
     return retval;
 }