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.

runtime/doc/Makefile

@@ -101,6 +101,7 @@ DOCS = \
 	tabpage.txt \
 	tagsrch.txt \
 	term.txt \
+	terminal.txt \
 	tips.txt \
 	todo.txt \
 	uganda.txt \
@@ -236,6 +237,7 @@ HTMLS = \
 	tabpage.html \
 	tagsrch.html \
 	term.html \
+	terminal.html \
 	tips.html \
 	todo.html \
 	uganda.html \