patch 9.1.0501: too complicated mapping restore in termdebug

Problem:  too complicated mapping restore in termdebug
Solution: simplify unmapping logic, add a few more tests
          (Ubaldo Tiberi)

closes: #15046

Signed-off-by: Ubaldo Tiberi <ubaldo.tiberi@google.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/version.c b/src/version.c
index 0e2e3ba..2d65eb2 100644
--- a/src/version.c
+++ b/src/version.c
@@ -705,6 +705,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    501,
+/**/
     500,
 /**/
     499,