patch 8.1.0370: not using internal diff if 'diffopt' is not changed

Problem:    Not using internal diff if 'diffopt' is not changed.
Solution:   Correct initialization of diff_flags. (Christian Brabandt)
diff --git a/src/version.c b/src/version.c
index 95fa7da..fc93cbf 100644
--- a/src/version.c
+++ b/src/version.c
@@ -795,6 +795,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    370,
+/**/
     369,
 /**/
     368,