patch 8.0.0957: a terminal job can deadlock when sending many keys

Problem:    When term_sendkeys() sends many keys it may get stuck in writing
            to the job.
Solution:   Make the write non-blocking, buffer keys to be sent.
diff --git a/src/version.c b/src/version.c
index f02af88..9d12b1e 100644
--- a/src/version.c
+++ b/src/version.c
@@ -770,6 +770,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    957,
+/**/
     956,
 /**/
     955,