patch 8.0.0712: the terminal implementation is incomplete

Problem:    The terminal implementation is incomplete.
Solution:   Add the 'termkey' option.
diff --git a/src/version.c b/src/version.c
index 6d448ae..5080e2c 100644
--- a/src/version.c
+++ b/src/version.c
@@ -765,6 +765,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    712,
+/**/
     711,
 /**/
     710,