patch 9.0.1078: with the +vartabs feature indent folding may use wrong 'ts'

Problem:    With the +vartabs feature indent folding may use wrong 'tabstop'.
Solution:   Use the "buf" argument instead of "curbuf".
diff --git a/src/version.c b/src/version.c
index a2b4e7e..1ce4042 100644
--- a/src/version.c
+++ b/src/version.c
@@ -696,6 +696,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1078,
+/**/
     1077,
 /**/
     1076,