patch 8.0.1566: too many #ifdefs

Problem:    Too many #ifdefs.
Solution:   Graduate FEAT_SCROLLBIND and FEAT_CURSORBIND.
diff --git a/src/gui.c b/src/gui.c
index 607a8fd..eac4fae 100644
--- a/src/gui.c
+++ b/src/gui.c
@@ -3959,9 +3959,7 @@
     int		sb_num;
 #ifdef USE_ON_FLY_SCROLL
     colnr_T	old_leftcol = curwin->w_leftcol;
-# ifdef FEAT_SCROLLBIND
     linenr_T	old_topline = curwin->w_topline;
-# endif
 # ifdef FEAT_DIFF
     int		old_topfill = curwin->w_topfill;
 # endif
@@ -4126,16 +4124,15 @@
     }
 
 #ifdef USE_ON_FLY_SCROLL
-# ifdef FEAT_SCROLLBIND
     /*
      * synchronize other windows, as necessary according to 'scrollbind'
      */
     if (curwin->w_p_scb
 	    && ((sb->wp == NULL && curwin->w_leftcol != old_leftcol)
 		|| (sb->wp == curwin && (curwin->w_topline != old_topline
-#  ifdef FEAT_DIFF
+# ifdef FEAT_DIFF
 					   || curwin->w_topfill != old_topfill
-#  endif
+# endif
 			))))
     {
 	do_check_scrollbind(TRUE);
@@ -4145,7 +4142,6 @@
 		updateWindow(wp);
 	setcursor();
     }
-# endif
     out_flush_cursor(FALSE, TRUE);
 #else
     add_to_input_buf(bytes, byte_count);
@@ -4474,9 +4470,7 @@
 	}
 	if (old_cursor.lnum != wp->w_cursor.lnum)
 	    coladvance(wp->w_curswant);
-#ifdef FEAT_SCROLLBIND
 	wp->w_scbind_pos = wp->w_topline;
-#endif
     }
 
     /* Make sure wp->w_leftcol and wp->w_skipcol are correct. */