patch 8.0.0693: no terminal emulator support

Problem:    No terminal emulator support.  Cannot properly run commands in the
            GUI.  Cannot run a job interactively with an ssh connection.
Solution:   Very early implementation of the :terminal command.  Includes
            libvterm converted to ANSI C.  Many parts still missing.
diff --git a/src/libvterm/t/90vttest_02-screen-1.test b/src/libvterm/t/90vttest_02-screen-1.test
new file mode 100644
index 0000000..003d56f
--- /dev/null
+++ b/src/libvterm/t/90vttest_02-screen-1.test
@@ -0,0 +1,18 @@
+# Test of WRAP AROUND mode setting.
+INIT
+WANTSCREEN
+
+RESET
+
+PUSH "\e[?7h"
+$REP 170: PUSH "*"
+
+PUSH "\e[?7l\e[3;1H"
+$REP 177: PUSH "*"
+
+PUSH "\e[?7h\e[5;1HOK"
+
+!Output
+$SEQ 0 2: ?screen_row \# = "********************************************************************************"
+          ?screen_row  3 = ""
+          ?screen_row  4 = "OK"