patch 8.0.1534: C syntax test fails when using gvim

Problem:    C syntax test fails when using gvim
Solution:   Force running in a terminal.  Check that 'background' is correct
            even when $COLORFGBG is set.
diff --git a/src/version.c b/src/version.c
index 95e5a72..085e0f9 100644
--- a/src/version.c
+++ b/src/version.c
@@ -779,6 +779,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1534,
+/**/
     1533,
 /**/
     1532,