patch 8.2.3666: libvterm is outdated

Problem:    Libvterm is outdated.
Solution:   Include patches from revision 769 to revision 789.
diff --git a/src/libvterm/t/17state_mouse.test b/src/libvterm/t/17state_mouse.test
index c39f56b..e5ba29b 100644
--- a/src/libvterm/t/17state_mouse.test
+++ b/src/libvterm/t/17state_mouse.test
@@ -170,3 +170,12 @@
   output "\e[?1006;2\$y"
 PUSH "\e[?1015\$p"
   output "\e[?1015;1\$y"
+
+!Mouse disabled reports nothing
+RESET
+  settermprop 1 true
+  settermprop 2 true
+  settermprop 7 1
+MOUSEMOVE 0,0 0
+MOUSEBTN d 1 0
+MOUSEBTN u 1 0