patch 8.0.1820: terminal window redirecting stdout does not show stderr

Problem:    Terminal window redirecting stdout does not show stderr. (Matéo
            Zanibelli)
Solution:   When stdout is not connected to pty_master_fd then use it for
            stderr. (closes #2903)
diff --git a/src/version.c b/src/version.c
index a6fd36a..7d86c01 100644
--- a/src/version.c
+++ b/src/version.c
@@ -762,6 +762,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1820,
+/**/
     1819,
 /**/
     1818,