patch 8.1.1271: compiler warnings for use of STRNCPY()

Problem:    Compiler warnings for use of STRNCPY(). (John Marriott)
Solution:   Use mch_memmove() instead of STRNCPY().
diff --git a/src/version.c b/src/version.c
index 8dee65e..0fa3c41 100644
--- a/src/version.c
+++ b/src/version.c
@@ -768,6 +768,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1271,
+/**/
     1270,
 /**/
     1269,