patch 8.0.0394: tabs are not aligned when scrolling horizontally

Problem:    Tabs are not aligned when scrolling horizontally and a Tab doesn't
            fit. (Axel Bender)
Solution:   Handle a Tab as a not fitting character. (Christian Brabandt)
            Also fix that ":redraw" does not scroll horizontally to show the
            cursor.  And fix the test that depended on the old behavior.
diff --git a/src/ex_docmd.c b/src/ex_docmd.c
index 4c52cdf..0bf940f 100644
--- a/src/ex_docmd.c
+++ b/src/ex_docmd.c
@@ -9812,6 +9812,7 @@
 
     RedrawingDisabled = 0;
     p_lz = FALSE;
+    validate_cursor();
     update_topline();
     update_screen(eap->forceit ? CLEAR : VIsual_active ? INVERTED : 0);
 #ifdef FEAT_TITLE