patch 8.1.2087: cannot easily select one test function to execute

Problem:    Cannot easily select one test function to execute.
Solution:   Support the $TEST_FILTER environment variable. (Ozaki Kiichi,
            closes #2695)
diff --git a/src/version.c b/src/version.c
index f08e5e0..0776a8a 100644
--- a/src/version.c
+++ b/src/version.c
@@ -758,6 +758,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    2087,
+/**/
     2086,
 /**/
     2085,