patch 9.0.0774: the libvterm code is outdated

Problem:    The libvterm code is outdated.
Solution:   Include libvterm changes from revision 802 to 817.  Revert some
            changes made for C89.
diff --git a/src/libvterm/t/13state_edit.test b/src/libvterm/t/13state_edit.test
index b435655..d3f3e9e 100644
--- a/src/libvterm/t/13state_edit.test
+++ b/src/libvterm/t/13state_edit.test
@@ -1,6 +1,6 @@
 INIT
 UTF8 1
-WANTSTATE se
+WANTSTATE seb
 
 !ICH
 RESET
@@ -242,6 +242,10 @@
   erase 0..25,0..80
   ?cursor = 1,1
 
+!ED 3
+PUSH "\e[3J"
+  sb_clear
+
 !SED
 RESET
   erase 0..25,0..80