patch 8.1.0827: missing dependency in Makefile

Problem:    Missing dependency in Makefile.
Solution:   Add dependency from autocmd.o on auto/osdef.h
diff --git a/src/version.c b/src/version.c
index 5510522..39a4f8f 100644
--- a/src/version.c
+++ b/src/version.c
@@ -784,6 +784,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    827,
+/**/
     826,
 /**/
     825,