patch 9.0.0912: libvterm with modifyOtherKeys level 2 does not match xterm

Problem:    libvterm with modifyOtherKeys level 2 does not match xterm.
Solution:   Adjust key code escape sequences to be the same as what xterm
            sends in modifyOtherKeys level 2 mode.  Check the value of
            no_reduce_keys before using it.
diff --git a/src/misc2.c b/src/misc2.c
index 3067414..4de94f3 100644
--- a/src/misc2.c
+++ b/src/misc2.c
@@ -1516,7 +1516,8 @@
  * CTRL-2 is CTRL-@
  * CTRL-6 is CTRL-^
  * CTRL-- is CTRL-_
- * Also, <C-H> and <C-h> mean the same thing, always use "H".
+ * Also, unless no_reduce_keys is set then <C-H> and <C-h> mean the same thing,
+ * use "H".
  * Returns the possibly adjusted key.
  */
     int
@@ -1525,7 +1526,12 @@
     if (modifiers & MOD_MASK_CTRL)
     {
 	if (ASCII_ISALPHA(key))
-	    return TOUPPER_ASC(key);
+	{
+#ifdef FEAT_TERMINAL
+	    check_no_reduce_keys();  // may update the no_reduce_keys flag
+#endif
+	    return no_reduce_keys == 0 ? TOUPPER_ASC(key) : key;
+	}
 	if (key == '2')
 	    return '@';
 	if (key == '6')