patch 8.2.1377: triggering the ATTENTION prompt causes typeahead mess up

Problem:    Triggering the ATTENTION prompt causes typeahead to be messed up.
Solution:   Increment tb_change_cnt. (closes #6541)
diff --git a/src/getchar.c b/src/getchar.c
index e040748..a8778e0 100644
--- a/src/getchar.c
+++ b/src/getchar.c
@@ -447,6 +447,8 @@
     typebuf.tb_silent = 0;
     cmd_silent = FALSE;
     typebuf.tb_no_abbr_cnt = 0;
+    if (++typebuf.tb_change_cnt == 0)
+	typebuf.tb_change_cnt = 1;
 }
 
 /*
diff --git a/src/version.c b/src/version.c
index 53e47bf..f5eb42b 100644
--- a/src/version.c
+++ b/src/version.c
@@ -755,6 +755,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1377,
+/**/
     1376,
 /**/
     1375,