patch 8.0.1639: libvterm code lags behind master

Problem:    Libvterm code lags behind master.
Solution:   Sync to head, solve merge problems.
diff --git a/src/libvterm/doc/URLs b/src/libvterm/doc/URLs
index 3a6512f..8380f5c 100644
--- a/src/libvterm/doc/URLs
+++ b/src/libvterm/doc/URLs
@@ -9,3 +9,6 @@
 
 Digital VT220 Programmer Reference Manual
   http://vt100.net/docs/vt220-rm/
+
+Summary of ANSI standards for ASCII terminals
+  http://www.inwap.com/pdp10/ansicode.txt
diff --git a/src/libvterm/doc/seqs.txt b/src/libvterm/doc/seqs.txt
index e5372d0..c26dc44 100644
--- a/src/libvterm/doc/seqs.txt
+++ b/src/libvterm/doc/seqs.txt
@@ -151,6 +151,7 @@
       DECSM 1000       = Mouse click/release tracking
       DECSM 1002       = Mouse click/release/drag tracking
       DECSM 1003       = Mouse all movements tracking
+      DECSM 1004       = Focus in/out reporting
       DECSM 1005       = Mouse protocol extended (UTF-8) - not recommended
       DECSM 1006       = Mouse protocol SGR
       DECSM 1015       = Mouse protocol rxvt