patch 9.0.0772: the libvterm code is outdated

Problem:    The libvterm code is outdated.
Solution:   Include libvterm changes from revision 790 to 801.
diff --git a/src/libvterm/t/62screen_damage.test b/src/libvterm/t/62screen_damage.test
index 32cac2d..3b1b238 100644
--- a/src/libvterm/t/62screen_damage.test
+++ b/src/libvterm/t/62screen_damage.test
@@ -152,4 +152,4 @@
 DAMAGEFLUSH
   moverect 1..25,0..80 -> 0..24,0..80
   damage 24..25,0..80
-  ?screen_chars 23,0,24,5 = "ABE"
+  ?screen_row 23 = "ABE"