patch 8.1.2145: cannot map <C-H> when modifyOtherKeys is enabled

Problem:    Cannot map <C-H> when modifyOtherKeys is enabled.
Solution:   Add the <C-H> mapping twice, both with modifier and as 0x08.  Use
            only the first one when modifyOtherKeys has been detected.
diff --git a/src/eval.c b/src/eval.c
index 0fe8fd3..ace1e01 100644
--- a/src/eval.c
+++ b/src/eval.c
@@ -3526,7 +3526,8 @@
 			  break;
 
 			    /* Special key, e.g.: "\<C-W>" */
-		case '<': extra = trans_special(&p, name, TRUE, TRUE);
+		case '<': extra = trans_special(&p, name, TRUE, TRUE,
+								   TRUE, NULL);
 			  if (extra != 0)
 			  {
 			      name += extra;