patch 8.1.1096: MS-Windows: cannot distinguish BS and CTRL-H

Problem:    MS-Windows: cannot distinguish BS and CTRL-H.
Solution:   Add code for VK_BACK. (Linwei, closes #1833)
diff --git a/src/term.c b/src/term.c
index c058171..ffc9884 100644
--- a/src/term.c
+++ b/src/term.c
@@ -663,6 +663,7 @@
     {K_K7,		"\316\366"},
     {K_K8,		"\316\372"},
     {K_K9,		"\316\376"},
+    {K_BS,		"\316x"},
 # endif
 
 # if defined(VMS) || defined(ALL_BUILTIN_TCAPS)