patch 8.1.0278: 'incsearch' highlighting does not accept reverse range

Problem:    'incsearch' highlighting does not accept reverse range.
Solution:   Swap the range when needed. (issue #3321)
diff --git a/src/version.c b/src/version.c
index a3f81f0..e1f2c6f 100644
--- a/src/version.c
+++ b/src/version.c
@@ -795,6 +795,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    278,
+/**/
     277,
 /**/
     276,