patch 9.1.0899: default for 'backspace' can be set in C code

Problem:  default for 'backspace' can be set in C code
Solution: promote the default for 'backspace' from defaults.vim to the C
          code (Luca Saccarola)

closes: #16143

Signed-off-by: Luca Saccarola <github.e41mv@aleeas.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/version.c b/src/version.c
index f83e597..7558bdc 100644
--- a/src/version.c
+++ b/src/version.c
@@ -705,6 +705,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    899,
+/**/
     898,
 /**/
     897,