patch 7.4.993
Problem:    Test 87 is flaky on AppVeyor.
Solution:   Reduce the minimum background thread count.
diff --git a/src/version.c b/src/version.c
index 9e77c6d..167f55b 100644
--- a/src/version.c
+++ b/src/version.c
@@ -742,6 +742,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    993,
+/**/
     992,
 /**/
     991,