bug#29002: it.first_visible_x is erroneously 0 while horizontal scrolling.

[Keith David Bershatsky]

The new fix relating to #29002 has an unintended side-effect of causing a full 
redisplay too often, e.g., when using isearch.

I am uncertain why the current Emacs design sets w->suspend_auto_hscroll to 
*true* every command loop, but that is what causes the new condition to force a 
thorough redisplay much more often than is actually needed.


          /* If the position of this window's point has explicitly
             changed, no more suspend auto hscrolling.  */
          if (w->suspend_auto_hscroll
              && NILP (Fequal (Fwindow_point (window),
                               Fwindow_old_point (window))))
            {

AUTO_STRING (my_string_one, "Hello world!");
CALLN (Fmessage, my_string_one);

              w->suspend_auto_hscroll = false;
              /* Force thorough redisplay of this window, to show the
                 effect of disabling hscroll suspension immediately.  */
              SET_FRAME_GARBAGED (XFRAME (w->frame));
            }