patch 9.0.0774: the libvterm code is outdated

Problem:    The libvterm code is outdated.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/26state_query.test b/src/libvterm/t/26state_query.test
index e4513de..41e7cf8 100644
--- a/src/libvterm/t/26state_query.test
+++ b/src/libvterm/t/26state_query.test
@@ -9,7 +9,7 @@
 !XTVERSION
 RESET
 PUSH "\e[>q"
-  output "\eP>|libvterm(0.2)\e\\"
+  output "\eP>|libvterm(0.3)\e\\"
 
 !DSR
 RESET