patch 8.0.0587: configure check for return value of tgetent skipped

Problem:    Configure check for return value of tgetent is skipped.
Solution:   Always perform the check. (Marvin Schmidt, closes #1664)
diff --git a/src/version.c b/src/version.c
index 3e683e8..7aae749 100644
--- a/src/version.c
+++ b/src/version.c
@@ -765,6 +765,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    587,
+/**/
     586,
 /**/
     585,