patch 8.2.0131: command line is not cleared when switching tabs

Problem:    Command line is not cleared when switching tabs and the command
            line height differs.
Solution:   Set the "clear_cmdline" flag when needed. (Naruhiko Nishino,
            closes #5495)
diff --git a/src/testdir/dumps/Test_cmdlineclear_tabenter.dump b/src/testdir/dumps/Test_cmdlineclear_tabenter.dump
new file mode 100644
index 0000000..27dcca5
--- /dev/null
+++ b/src/testdir/dumps/Test_cmdlineclear_tabenter.dump
@@ -0,0 +1,10 @@
+| +8#0000001#e0e0e08|+| |[|N|o| |N|a|m|e|]| | +2#0000000#ffffff0|[|N|o| |N|a|m|e|]| | +1&&@49|X+8#0000001#e0e0e08
+> +0#0000000#ffffff0@74
+|~+0#4040ff13&| @73
+|~| @73
+|~| @73
+|~| @73
+|~| @73
+| +0#0000000&@74
+@75
+@57|0|,|0|-|1| @8|A|l@1|